At least five people have been killed in a series of blasts targeting a complex housing Pakistani intelligence and security forces in the southern town of Sukkur in Sindh province, state TV has said.

Forty people were wounded in Wednesday'a attack in which 10 gunmen raided the heavily guarded compound and detonated four bombs, said Masood Bangash, the deputy superintendent of police in Sukkur.

Bangash said the local offices of the Inter-Services Intelligence, the Pakistani military intelligence force, seemed to be the main target. 

Four explosions were heard in the area, where "terrorists" seized control of one government building and another building was under fire, Pakistan's PTV reported.

Al Jazeera's Kamal Hyder, reporting from the capital Islamabad, said the first attack happened after iftar, the evening hour when Muslims observing the holy month of Ramadan break their fast.

He said a vehicle laden with explosives is said to have entered a maximum-security area, and the target was the intelligence office.

"After the explosion the entire area was plunged into darkness. A number of suicide bombers are said to have struck after that explosion and a lot of gunfire was heard," said our correspondent.

"The security forces have cordoned off the area [and] many of the houses have collapsed because of the sheer force of that first blast and rescue efforts are still under way."

Source: Agencies