MIRANSHAH (AFP) - A US drone strike targeting a vehicle in North Waziristan Agency killed four militants on Tuesday, local security officials said. The missile attack, the second in two days, took place near Qutub Khel village, five kilometres east of Miranshah, the main town in North Waziristan Agency. Two missiles were fired from a US drone targeting a militant vehicle. So far, four militants were killed, a security official said. Another security official in the area confirmed the attack and the toll. In a strike on Monday two drone missiles killed at least four militants in South Waziristan. The United States does not officially confirm Predator drone attacks, but its military and the CIA operating in Afghanistan are the only forces that deploy the armed, unmanned aircraft in the region. More than 20 US drone strikes have been reported in Pakistan since May 2, when US elite forces killed Al-Qaeda chief Osama bin Laden. Drone attacks are unpopular among the Pakistani public, which is opposed to the governments alliance with Washington and sensitive to perceived violations of sovereignty.