Nine people, including six army men, were killed when unidentified gunmen ambushed a van ferrying security personnel in Pakistan's Balochistan province, hours after the visit of top US envoy Richard Boucher to the troubled region.

The victims in the shooting which took place before midnight on Thursday included one policeman and two civilians.

A man called up the Quetta Press Club and claimed the killings were carried out by the outlawed Balochistan Liberation Army, a separatist group in the province that is fighting the government forces for a greater share in the region's rich natural resources.

Major General Waheed Arshad, head of Inter-Services Public Relations, confirmed in a statement that six army personnel had been killed in the ambush and blamed it on anti-state elements.

A full-scale investigation would be carried out into the attack that also wounded four on a busy road outside the city's main railway station, he said.

Arshad said according to initial information the servicemen were returning from leave when their van was ambushed by unknown gunmen.

One of those killed was a policeman while one wounded was in critical condition, senior police official Rehmatunna Niazi said.

The attack came just hours after a visit by top US envoy Richard Boucher who made a stopover during a visit to the border region to check on the efforts by Pakistan to curb Taliban and Al Qaeda [Images] militants.