DHAKA, Bangladesh — The police in Bangladesh announced on Friday that they had killed Nurul Islam Marzan, who was suspected of guiding a team of militants through the deadly siege of a fashionable Dhaka restaurant last year, in an early morning gunfight.

Mr. Marzan was a close aide to Tamim Ahmed Chowdhury, who had been identified as the top coordinator in Bangladesh for the Islamic State and the leader of a newly founded branch of the domestic militant network Jama’atul Mujahedeen Bangladesh.

The Bangladeshi authorities said Mr. Chowdhury planned the attack in July at the restaurant, the Holey Artisan Bakery. He was killed in August in a shootout.

The police said the two men worked intensively with the team of five assailants who burst into the restaurant and singled out foreigners and non-Muslims inside. Twenty Bangladeshi and foreign hostages and two police officers were killed, the most ambitious attack undertaken by Islamist insurgents in the region in recent years.