USAF photo of a MQ-1L Predator UAV (unmanned aerial vehicle) armed with AGM-114 Hellfire missiles, 2006 file photo

Pakistani officials say a suspected U.S. drone fired missiles at a house in northwest Pakistan, killing at least six people.  Officials say foreign militants are among the dead.

The incident occurred in North Waziristan, a tribal region bordering Afghanistan and a known stronghold for Taliban and al-Qaida militants.

Suspected U.S. strikes into Pakistan have become a point of contention in recent weeks. Pakistan's president, Asif Ali Zardari, has called the alleged raids a violation of Pakistan's sovereignty.

Separately, officials said Pakistani troops backed by helicopter gunships killed 13 Taliban militants in the northwestern Bajaur tribal region.

The Pakistani military is trying to drive out militants accused of making deadly attacks inside Pakistan and in neighboring Afghanistan.

Last week, Pakistan's military said it had killed at least 1,000 militants since launching the offensive in Bajaur in August.  It said more than 60 soldiers have been killed.

Elsewhere Tuesday, Pakistani police said a landmine blast killed at least two soldiers and wounded four others in southwestern Baluchistan province.

Ethnic Baluch tribesmen have been waging an insurgency in Baluchistan to press for a greater share of profits from the region's natural resources.  Taliban militants also are known to be active in the province.

Some information for this report was provided by AFP, AP and Reuters.