Bangladesh's operations to chase Islamist militants from a five-storey building in Sylhet could last long as there are several more "well-trained operatives" inside the hideout, said military of the country on Monday.

Eight persons have been killed so far in the 'Operation Twilight'. The military operation entered its fourth day on Monday 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.

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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.