Suspected Al-Qaeda militants killed six Yemeni soldiers in clashes in the south on Wednesday as a security official told AFP that a US drone had struck a makeshift checkpoint killing three jihadists. Six soldiers were also wounded as they advanced on the Abyan provincial capital of Zinjibar, most of which has been in the hands of the the Partisans of Sharia (Islamic Law) group since May, military and medical officials said. The army has been engaged in a major offensive to retake Zinjibar and a commander told AFP that troops had moved to within a kilometre (less than a mile) of the city's outskirts after fierce clashes which killed four soldiers and wounded more than a dozen on Tuesday. A local security official told AFP that a US drone strike against a suspected Al-Qaeda checkpoint in the Abyan village of Mihfed had killed three militants and wounded two. There was no immediate confirmation of the strike from Washington but Central Intelligence Agency director Leon Panetta said in June that the United States was carrying out counter-terrorism operations in Yemen. Abyan residents report almost daily overflights by US drones, although the Yemeni government has repeatedly denied that Washington has played more than a supporting intelligence role in operations on its territory. In June, the New York Times reported that Washington had resumed air strikes in Yemen after suspending them for a period because poor intelligence had led to civilian deaths. The paper said Washington had started deploying manned aircraft as well as drones in the operations. Since anti-government protests swept Yemen in late January, militants have taken advantage of the weakening of central authority to set up base in several southern provinces as well as Maarib province in the east. Washington and other Western governments have expressed growing concern about the role Al-Qaeda might play in Yemen if the regime of veteran President Ali Abdullah Saleh collapses and a power vacuum ensues.