Two Afghans opened fire on a police commander at a checkpoint in a remote district in the country's south, killing him and six of his men, officials said Tuesday.

The police chief of volatile Kandahar district said that the two attackers were former policemen who had rejoined the force only two days previously. Gen. Abdul Razaq said they fled in a police vehicle with their dead comrades' weapons after the attack in the remote district of Arghistan late Monday.

Ahmad Jawed Faisal, spokesman for the governor of Kandahar province, said the two were dinner guests invited by the commander to eat with him at his checkpoint. He said they picked up weapons after dinner and opened fire.

It was impossible to immediately reconcile the two accounts.

Taliban insurgents have warned they would infiltrate Afghan security forces to conduct what the international military coalition calls "insider attacks." There have been several such attacks in the past year, including officers poisoned while eating.

Also Tuesday, a roadside bomb under a bridge hit an Afghan lawmaker's convoy on a major highway north of Kabul, killing five people.

Lawmaker Obaidullah Ramin from northern Baghlan province said he does not believe he was intentionally targeted by the explosion early Tuesday. Police confirmed his account.

He said the main highway leading north out of Kabul is often mined by Taliban insurgents to target official-looking convoys.

Three of Ramin's relatives were among the dead.

Roadside bombs are a favorite Taliban weapon to target government officials as well as the both Afghan and international military forces.

The insurgents have stepped up attacks in recent weeks, seeking to weaken the government and security forces as foreign troops pull back in preparation for the international coalition leaving next year.