MIRANSHAH (Agencies) - A US drone attack destroyed a vehicle in North Waziristan on Friday, killing at least four suspected militants, security officials said. Two missiles slammed into the vehicle in the semi-autonomous northwestern district considered the heartland of militants and the focus of a dramatic increase in US drone strikes since early September. Officials reported the attack as US President Barack Obama and NATO leaders flew to Lisbon for a summit designed to set a date to hand control of the fight against the Taliban in Afghanistan to local forces in 2014. Two missiles were fired on a vehicle. So far four militants are confirmed killed in this attack, a senior security official said on condition of anonymity. Local intelligence officials said the dead belonged to the Taliban and Al-Qaeda linked Haqqani network, but it was not immediately clear whether they included any high-value targets. They said up to four militants were killed when the vehicle exploded into a fireball in Naurak village, about 15 kilometres east of Miranshah, the main town in North Waziristan. Fridays drone strike comes three days after a similar attack killed at least 20 militants and destroyed a training centre north of Miranshah.