A roadside bomb killed six Taliban militants, including a prominent local commander, in northwestern Pakistan on Thursday, an attack that could have been motivated by tensions between different insurgent groups.

The bomb was detonated by remote control as Hakim Khan and five lower ranking militants were driving through the town of Marindy in the Kurram tribal region, said Jamil Khan, a local administrator. The commander who was killed was suspected of attacking Pakistani troops and kidnapping people for ransom, he said.

It was unclear who carried out the attack, but rivalries between different groups of fighters in northwestern Pakistan sometimes escalate into violence.

The slain commander was from Kurram but had close ties to the Pakistani Taliban, an umbrella group of militants that is based in nearby North and South Waziristan and has declared war on the Pakistani state, Khan said.

A German citizen of Afghan descent was the source of much of the information on a potential "Mumbai-style" terror plot in Europe, a German counterterrorism official said Wednesday.

The man, Ahmed Sidiqi, was detained in Kabul in July and transferred to U.S. custody where he has "revealed details about the terror plot," said the official, who did not want to be named because he is not authorized to talk to the media.