KABUL - Pakistan's peace talks with extremists have resulted in a 40 per cent rise in rebel activity in Afghanistan, where there are more foreigners on the battlefield, Nato and Afghan forces said Wednesday. It is up to the international community to put pressure on Pakistan to root out the "cause" of the unrest, with Nato's military force not able to pursue militants over the border, spokesman Captain Mike Finney told reporters. Afghanistan has seen a spike in insurgency-linked violence in recent weeks, with more attacks by Taliban-linked rebels, including against troops with Nato's International Security Assistance Force (Isaf). Finney said the warmer weather had also played some part. "There is also evidence that the activities increased by some 40 per cent since ... tribal areas became unregulated following the negotiations between the Pakistan government and (leader of local Taliban) Baitullah Mehsud," he said. Mehsud has vowed to continue "jihad" in Afghanistan even while pursuing peace talks with Islamabad. "But the Isaf mandate is very clear, and that goes as far as the border," Finney said. "In terms of fighting the cause, that is for the international community to put pressure on those who can do something about it." Afghan Defence Ministry spokesman Mohammad Zahir Azimi said meanwhile the number of foreign militants in Afghanistan had increased, with insurgents changing tactics from targeting security forces to focusing on infrastructure. "In the past the attacks were mostly on Afghan and foreign forces. Now we see they target vital and basic infrastructure," Azimi said at the joint Press conference with Finney. The military had reports of militants planning attack on power plants and dams and they were already striking highways and construction projects, he said. Foreign fighters were identified through documents found on their bodies and the languages they used, he said.