U.S. and Iraqi officials say a car bombing has killed at least 10 people and injured at last 20 in the northern Iraqi town of Tal Afar.

U.S. military officials say the explosion occurred Saturday near an auto dealership.

Tal Afar is in volatile Nineveh province, and its capital Mosul, some 400 kilometers north of Baghdad, is said to be one of the last strongholds of al-Qaida fighters in Iraq.

Violence there has fallen in recent months but attacks are still common in some parts of the country.

On Friday, Iraqi Shi'ite cleric Moqtada al-Sadr reiterated calls for the U.S. to remove its troops and bases from Iraq or face a new wave of attacks.

Sadr says he will activate a new militia, called "The Promised Day Brigade," to fight American forces.  

The cleric also urged his supporters to demonstrate against a proposed U.S.-Iraqi security pact that could allow U.S.-led forces to remain in Iraq after the United Nations mandate expires at the end of this year.

Iraq's ambassador to the U.N., Hamid al-Bayati, said Friday in New York, he is optimistic an agreement will be reached.

Meanwhile, the U.N.'s top envoy to Iraq says provincial elections scheduled for early next year are on track. But Staffan de Mistura told the the U.N. Security Council Friday that spoilers might try to use violence to derail the vote.

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