Bangladesh's military today said their operations to flush out Islamist militants from a five-storey building in Sylhet could last long as there are several more "well-trained operatives" inside the hideout. Eight persons have been killed so far in the 'Operation Twilight'. The military operation entered its fourth day today in this northwestern city, about 236 km from the capital, Dhaka. After a relative lull since last night, sporadic gunfire and explosions could be heard today from the five-storey building in Sylhet. The military launched 'Operation Twilight' to flush out the militants from the hideout. Locals said they could hear burst of automatic weapons and explosions once again after 6 am. "We heard sporadic gunshots and explosions," a resident in the northeastern city told PTI. "There are several more well-trained operatives active inside the hideout," Brigadier Gen Fakhrul Ahsan told a media in Sylhet. He said that the assault was far from over and pointed to "considerable risks" involved in it. Ahsan added that the militants were equipped with small arms, explosives and grenades and laid out booby traps at different corners of the building creating a situation which slowed down the operations progress at the building. "The entire area has become risky. Considering the overall situation, it will take more time for the operation to complete," he said. You may also like to watch: The operation was launched after a suicide bomber on Friday night blew himself up at the international airport in Dhaka in an attack claimed by the ISIS. It came a week after an identical attack on a RAB camp in Dhaka. On Saturday, two powerful bombs ripped through a crowd near the hideout, killing six people, two being police officers and injuring about 50, including two army officers currently serving the elite anti-crime Rapid Action Battalion (RAB). Army said the two militants blew themselves up detonating suicide vests after being shot by army commandos on ground floors of building but "we assume more militants are there inside". Bangladesh has rejected the Islamic State terror group's presence in the country after it claimed the responsibility for Saturday's retaliatory attack. Meanwhile, residents who lived in the building where operation is taking place said they were virtually taken hostage with militants warning them of bombs implanted on their way out The commandos brought them out from the top of the building making their way there from the rooftop of an adjacent structure. Banker Ranajit Das, a tenant of the house who was evacuated along with his five family members, said militants' warnings prevented them from coming out until commandos evacuated them from the building. "They (militants) said bombs were implanted downstairs which would blow us up if we try to leave," he said. Para-commandos evacuated civilians from the top floor of the building placing roof to roof ladders from an adjacent building moved out residents from one floor after another until they reached the second floor stairwell where they found improvised explosive devices placed on the stairs. Bangladesh has been witnessing a spate of attacks on secular activists, foreigners and religious minorities since 2013. The country launched a massive crackdown on militants specially after the Dhaka cafe attack.