PESHAWAR (AFP) Security officials said Tuesday that five people were killed and two wounded by NATO cross-border fire from Afghanistan in the third such incident in days. They said members of the US-led International Security Assistance Force (ISAF) in the eastern Afghan province of Khost shelled Matta Sanga town close to the border early Monday. Five people were killed and two injured in the shelling by NATO-led forces, a security official told AFP on condition of anonymity. A government official in the region said the casualties were all civilians. A military official, who also spoke to AFP on condition of anonymity, also confirmed the incident. ISAF spokeswoman Major Sunset Belinsky confirmed an engagement by ISAF helicopters against insurgent forces on the Pakistan border Monday. According to current reports the helicopters did not enter Pakistan airspace. ISAF forces attempted to contact the Pakistan military prior to the engagement, but were unable to make contact, Belinsky said. The spokeswoman did not have any information about casualties. Pakistan on Monday denounced cross-border airstrikes by NATO helicopters pursuing militants as a violation of its sovereignty after ISAF said it killed more than 30 rebels on Friday. ISAF said the helicopters opened fire after a remote Afghan forces outpost in Khost province came under attack, and that two helicopters returned to the border area on Saturday, killing several more insurgents.