CARACAS, Venezuela — The shadowy underworld of Basque exiles in this city is coming under sharp scrutiny after recent arrests in Europe and an indictment this month from one of Spain’s top judges asserting that Venezuelan intelligence officials were involved in training Basque separatists and Colombian guerrillas in Venezuela.

Paintings for sale in front of Bar Basque, a restaurant known for its fine seafood as well as for being frequented by politically active artists and intellectuals in Caracas, Venezuela.

Venezuela has lured thousands of Basque immigrants since the 1930s, when some began fleeing persecution in Franco’s Spain. Spanish intelligence specialists say the armed Basque separatist group ETA has maintained a cell in this community since 1959, formed just months after ETA’s creation in Spain. The indictment issued on March 1 by Judge Eloy Velasco of Spain’s National Court opened a rare window into ETA’s activities here, naming Arturo Cubillas, 45, a Basque exile, as ETA’s leader in Venezuela.

The indictment also said that Mr. Cubillas received assistance from Venezuela’s military intelligence agency, led by Gen. Hugo Carvajal. The United States Treasury Department in 2008 identified General Carvajal as a supporter of the Revolutionary Armed Forces of Colombia, or the FARC, after reports detailed how he provided weapons for the Colombian rebel group.

Inside the somewhat hermetic Basque community here, which mixes at its own social club and at a handful of small restaurants like Bar Basque and Urrutia, which offer specialties like Txistorra sausages and Txakolí wine, the indictment has brought uncomfortable attention.

Many in the Basque community, which numbers in the low thousands and includes prominent entrepreneurs and scholars, disavow ETA’s tactics. Basques here are also divided between those who oppose President Hugo Chávez and those who support him, with some exiles tied to ETA in the pro-Chávez camp. Some Basques expressed fear of publicly discussing ETA, while others acknowledged the complexity surrounding Mr. Cubillas and dozens of others with links to ETA.

“Some in this group exist in a light-colored gray area and others in a gray area that is darker,” said Carlos Otaño, 74, a psychologist who is president of Centro Vasco, the city’s oldest Basque club. “Nothing is simple with ETA,” said Mr. Otaño, who said he had known Mr. Cubillas for years.

Mr. Cubillas was part of a group of ETA operatives deported from Algeria after failed peace negotiations between the group and the Spanish government. An informal agreement between the presidents of Spain and Venezuela allowed the exiles to seek refuge in Caracas.

Mr. Cubillas quickly put down stakes, according to other Basque exiles in Venezuela. Trained as a chef, he opened his own Basque cafe called Oker’s, and later managed the restaurant at Centro Vasco. Later, he joined Mr. Chávez’s political movement, eased by his marriage to Goizeder Odriozola, a pro-Chávez journalist and daughter of Basque immigrants. Despite being tied to three murders carried out by ETA in Spain in the 1980s, Mr. Cubillas was appointed in 2007 as security director at the National Land Institute, which oversees land expropriations.

His wife also climbed steadily in the elite echelons of Mr. Chávez’s government. She now works as a senior aide to Vice President Elías Jaua.

Neither Mr. Cubillas nor Ms. Odriozola responded to requests for interviews.

The indictment from Judge Velasco, which seeks the arrest of 13 militants belonging to ETA and the FARC, has revived calls in the United States for Venezuela to be added to the State Department’s list of state sponsors of terrorism.

Such a designation seems unlikely because it could affect Venezuela’s resilient trade with the United States and Spain. Venezuela’s government has denied collaborating with ETA.

Despite the current tension, the allure of Caracas for ETA militants is cemented in Venezuela’s historically warm dealings with Spain’s Socialist Party, which has governed Spain throughout most of its democratic history since Franco’s death in 1975.

The biggest waves of ETA operatives arrived here in the 1980s, from France and Algeria, and from Panama in 1990.

Other Latin American cities, notably Mexico City, have absorbed a number of ETA members. But Spanish concerns focus largely on those in Venezuela.

“It’s not the biggest ETA colony, but it is the most important one in qualitative terms,” said Óscar Elía, an ETA expert with the Madrid-based Strategic Studies Group. “Venezuela is where they enjoy the biggest liberty.”

Since Mr. Chávez rose to power 11 years ago, clandestine movements and relocations of militants from Mexico and Cuba to Venezuela have increased, and there are now dozens of ETA militants living in Venezuela, according to Mr. Elía and other Spanish intelligence specialists.

In its 50-year campaign for a separate homeland for the Basque people of Spain and France, ETA has killed more than 800 people. In recent years, French and Spanish authorities have cooperated closely, infiltrating the group and arresting some senior leaders.

The arrest of three high-level ETA militants in France last month further exposed the group’s roots here. Along with ETA’s top military leader, Ibon Gogeaskoetxea, French officials arrested José Lorenzo Ayestarán, 52, who was among a group of ETA militants deported here by France in the 1980s. He was wanted in Spain in connection with eight killings.

In 2006, Mr. Chávez’s envoy to the Inter-American Court of Human Rights negotiated a deal to give Venezuelan citizenship to several ETA members, including Mr. Ayestarán, but the deal was scrapped. Mr. Ayestarán, implicated by Spain’s Interior Ministry in an abduction plot at the time of his arrest, lived in Venezuela until last year.

In a separate episode, the Portuguese police arrested Andoni Zengotitabengoa, a who is suspected of being an ETA militant, as he tried to board a Caracas-bound flight in Lisbon on Thursday, after officials said they detected his fake Mexican passport. He is among two escaped ETA suspects who set up a bomb-making shop in Óbidos, Portugal, before authorities raided the home and found the explosives.

Some of the most chilling revelations of ETA’s Venezuelan ties involve Mr. Cubillas.

Judge Velasco’s indictment, based largely on testimony from demobilized FARC guerrillas and FARC computer files obtained by Colombia’s army, describes a 20-day training course led by Mr. Cubillas in 2007 in Apure State for 13 FARC rebels and 7 members of a smaller Venezuelan guerrilla group, the Bolivarian Liberation Front.

Judge Velasco said Mr. Cubillas organized the course, with the assistance of other ETA militants, in which they instructed the guerrillas on explosives. The indictment described how Mr. Cubillas was accompanied by a Venezuelan official identified as a military intelligence agent.

One message between FARC commanders from 2003, cited by Judge Velasco, describes an earlier course in Venezuela where four ETA members received guerrilla training from the FARC. “The friends from Navarre and Bilbao are in the final phase,” it said. “They are happy.”

Simon Romero reported from Caracas, and Andrés Cala from Madrid. María Eugenia Díaz contributed reporting from Caracas.