Pakistani intelligence officials say a suspected U.S. drone strike has killed at least four militants in the country's northwest tribal region.

The officials said the unmanned aircraft fired missiles Thursday at a vehicle in South Waziristan.

The United States does not publicly acknowledge the use of drone strikes against Taliban and al-Qaida-linked militants in Pakistan's northwest. Pakistani officials have protested the attacks as a violation of the country's sovereignty.

Also Thursday, police said a bomb exploded in a popular market in Peshawar, wounding at least seven people.

Authorities said the explosives were packed in an oil canister.

No one immediately claimed responsibility for the blast, which damaged several nearby shops.

Peshawar is the capital of Khyber-Pakhtunkhwa province near the Afghan border, and has experienced numerous suicide and bomb attacks in recent years linked to the Taliban and al-Qaida.