SARAJEVO, Bosnia and Herzegovina - A recent police raid on an apartment near this city's airport uncovered evidence of an imminent suicide bombing, intensifying the fears of Western security services that Bosnia is becoming a haven for Islamic militants.

The raid, which occurred in October after an extensive surveillance operation by both the Bosnian police and Western intelligence services, turned up an arsenal in the apartment, in the suburb of Ilidza, including suicide vests, up to 65 pounds of exploding bullets and high explosive, and a machine pistol. Investigators also found a video in which three men - at least two of them teenagers - are seen asking forgiveness from God for their "sacrifice," in a recording made just hours before the raid. The two teenagers were detained.

[Subsequent investigations by the Bosnian police led to the arrests of three more men, all Bosnians, whose identities have not been disclosed. Two were arrested on Nov. 19 and accused of providing support for the Ilidza group. The last was detained on Nov. 24 and charged with supplying explosives. The police also say they seized 22 pounds of explosives kept by the same man in a forest in Hadjici, just outside Sarajevo.]

The weapons seizures and arrests, most notably of the two men found in the Ilidza apartment - a Turk who had been living in a well-established Muslim community in Denmark, and a Swede of Bosnian heritage - have provided government and international officials here with the clearest evidence in years of a terrorist cell working in Bosnia. They have also shed light on a complex web that stretches well beyond the Balkans and that may threaten Western Europe.

Diplomats and international officials close to the investigation describe it as a series of overlapping networks, in which young Muslims from Scandinavia have been recruited as possible suicide bombers and sent to Bosnia. Government officials here say the group in Bosnia used the former Yugoslav state as a staging ground for attacks elsewhere in Europe.

Dragan Mektic, Bosnia's deputy security minister, said in an interview that "all the indicators show that Bosnia is a territory where they can come and rest, organize their activities, and then go and carry out" an attack elsewhere,

The police have accused two of the Bosnian suspects with planning an attack in "internationally protected property," a commonly used law enforcement euphemism for an embassy. But senior Western diplomats and Mr. Mektic emphasized that there were no indications that the target of the Ilidza cell was in Bosnia.

The surveillance began in late September, Mr. Mektic said, and focused on at least 10 people, some of them from the region, others Bosnian passport-holders with ties to the Middle East. During that time, five of the people rented the apartment in Ilidza, as well as rooms in a house in Hrasno Brdo, a rambling hilltop suburb of Sarajevo.

When the police finally moved to make arrests, they initially captured only 3 of the 10. The third - who was not on the suicide tape - had rented the apartment in Ilidza on the others' behalf. He was dropped from the investigation.

The potential for Bosnia to become a terrorist base has long been a concern of security services, both Western and Bosnian. The 1992-95 conflict here ripped apart Bosnia's Muslim, Serbian and Croatian populations, opening the way for illicit weapons supply lines and organized crime. The religious and ethnic overtones of the war attracted, at minimum, dozens of Muslim fighters from the Middle East, many with experience of fighting the Russians in Afghanistan, who brought with them the influence of radical Islam.

Many of those fighters settled here and married Bosnian women. They have remained largely at the margins of the Islamic community. While more conservative, they have not had a significant impact on Bosnia's Muslims, who by and large are moderate in their religious outlook.

Periodically, former fighters and others who came to Bosnia to help Muslims have been placed under investigation by Western and Bosnian security services, which say they have thwarted several terrorist attacks as a result.

In January 2002, six Algerians living in Bosnia were accused of plotting an attack on the American Embassy in Sarajevo. No evidence of the alleged plot was made public, and a Bosnian court dismissed the charges and ordered the men released. But the Bosnian government, under the pressure from the United States, transferred them to American custody. They were flown to Guant?namo Bay, Cuba, where they remain.

Bosnia gave passports to more than 800 former fighters and aid workers from the Middle East. Both the United States and Saudi Arabia have accused Bosnia of giving passports to known terrorists, sometimes under aliases.

Few details have been disclosed about those believed to be coordinating the Sarajevo group, but Mr. Mektic and international officials close to the investigation say Bosnia's liberal passport policy as well as its porous borders made it appealing as a terrorist base, in spite of the presence of several thousand European Union-led peacekeepers. (The passport process has been made more stringent.)

"The flow of people, narcotics and other materials is very difficult to break," said Jonathan Ratel, a prosecutor responsible for organized crime in Bosnia's State Court.

The background of the two men in custody has helped investigators make connections between the operation here and the rest of Europe.

Abdulkadir Cesur, 18, and Mirsad Bektasevic, 19, were arrested in the raid near the airport. Both traveled to Bosnia three weeks earlier, according to Bosnian border police records, and come from Muslim communities in Denmark and Sweden. Mr. Cesur is Turkish but has Danish residency, and Mr. Bektasevic left Bosnia at the age of 6 and became a Swedish citizen.

Acting on phone records, a senior international official close to the Bosnian investigation said, the Bosnian police tipped off their counterparts in Denmark about the possibility of a parallel group in Copenhagen.

On Oct. 27, the police in Denmark, working in liaison with the Bosnian authorities, arrested four men all between the ages of 16 and 20 and seized computers, computer discs, books with radical Muslim literature and Danish kroner worth some $32,000, from separate addresses. Since then, three more people have been detained in connection with the Bosnian arrests. Out of the seven, none of whom have been identified, six attended the same mosque in the Noebbro district of Copenhagen.

One international official close to the investigation, who spoke on condition of anonymity because the case is formally the responsibility of Bosnia's state prosecutor, said the group had sought to recruit potential suicide bombers from established immigrant communities in the West.

"They are indoctrinated into thinking that they could be a huge cause for their people," the official said. "They are young and impressionable and potentially disenfranchised from the society they find themselves living in."

Mr. Bektasevic's background appears to fit that description. Unemployed since leaving school a year and half ago, he had begun to attend a mosque in Gothenburg, the city nearest their home on Sweden's west coast, according to his mother, Nafija Hamedovic. She described her son as having come under the influence of three men: a Palestinian from Syria, a Kurd and a Somali.

"He was not religious before, but in the past two years he practiced more seriously," Mrs. Hamedovic said in a telephone interview.

"Some people frightened him and talked to him about hell, and told him would be tortured in hell if he does not pray and does not believe," she said.

But she dismissed accusations that he could have been a suicide bomber, explaining that he had gone to stay with her relatives in Sarajevo and that he obviously had no outside support.

"It's a lie," she said. "He didn't even have any money. I even had to pay for his bus ticket to Bosnia."