Gunmen on a motorbike shot dead a police officer in south Yemen on Thursday, a security official said, a day after three senior air force pilots were killed in a similar Qaeda-style attack. "Two gunmen on a motorbike intercepted the police officer, a member of the political security services," in Huta, the provincial capital of Lahij, said the official. He said one of the two gunmen opened fire at the officer, killing him instantly, adding that the assailants fled the scene. "Al-Qaeda could be behind the attack," he said. Thursday's assassination comes one day after suspected Al-Qaeda gunmen on a motorbike shot dead three air force officers from the strategic Al-Anad air base in Lahij, according to army sources. Al-Qaeda was driven out of most of its strongholds across south Yemen in an army offensive backed by US drone strikes last year. The weakened militants have withdrawn to mountainous regions in several provinces. Although weakened, police and army officers come under frequent hit-and-run attacks, with authorities blaming Al-Qaeda for the assaults which are usually carried out by gunmen on unregistered motorbikes. In a bid to clamp down on the increasing number of such attacks, authorities earlier this year launched a campaign ordering unlicensed bikes off the streets. Residents said militants linked to the Al-Qaeda affiliated Ansar al-Sharia group have been distributing posters and leaflets in several towns across Lahij and Hadramawt provinces in the southeast, threatening members of the security forces and urging jihad holy war. "Ansar al-Sharia are coming," read graffiti scrawled in Huta.