GAZIPUR, Bangladesh, Dec. 5 - A man suspected of masterminding two suicide bombings aimed at legal offices here last week was arrested Monday.

The attacks, on Nov. 29 at a law office, and on Dec. 1 at a government office where lawyers were planning to meet, left 10 people dead, including one of the bombers, and wounded nearly 90. The victims included Anwarul Azim, the assistant general secretary of the Gazipur Bar Association, who died of his wounds on Monday.

The authorities did not link the arrest to another attack on Nov. 29, in Chittagong, in which a suicide bomber struck a courthouse, killing himself and 2 other people, and wounding 17.

The police said the man taken into custody early Monday was seized at his home as he prepared a bomb for an attack on Monday morning.

He was identified as Enyatullah Ujjal, 26, a district leader of Jamaat ul-Mujahedeen Bangladesh, or the Bangladesh Assembly of Holy Warriors, a banned Islamist organization that the authorities link to the increasing violence here.

"Today we have caught the most important criminal, a top terror in the area," said the assistant superintendent of police here, Monir Uddin. "He is a very active member of the suicide squad."

Mr. Uddin added that the police had also found a large supply of materials for making bombs when they arrested Mr. Ujjal after being told of his activities and whereabouts.

Mr. Ujjal, the police said, confessed to making the bombs used in both attacks in Gazipur, and to giving one of the bombs directly to Abdur Razzak, who was wounded carrying out the attack on Dec. 1.

The police said they arrested 26 people on Monday afternoon based on information provided by Mr. Ujjal. Nearly 180 suspects, including several believed to belong to Jamaat ul-Mujahedeen Bangladesh, have been detained in connection with the suicide bomb attacks last week.