ISLAMABAD - Prime Minister Syed Yousuf Raza Gilani called on President Asif Ali Zardari here at Aiwan-e-Sadr on Saturday. Foreign Minister Hina Rabbani Khar was also present during the meeting. The prime minister and president discussed the situation arising out of the firing incident by Nato and Isaf helicopters and fighter aircraft on two Pakistani border posts in Mohmand Agency that resulted in the loss of security forces officials. Condemning the incident, President Zardari demanded an immediate action from Nato/Isaf forces against those responsible for the aggression. The president said the attack was unacceptable which resulted in loss of precious lives of Pakistani troops. Meanwhile, Ambassador Munter has expressed regret for the loss of life in cross-border incident, a statement issued by the US Embassy said. I have seen press accounts of an incident on the Pakistani-Afghan border in which Pakistani soldiers were reportedly killed. I regret the loss of lives of any Pakistani servicemen, and pledge that the United States will work closely with Pakistan to investigate this incident, the statement quoted US envoy as saying.