At least fourteen Iraqis were killed by US troops during the clashes with supporters of Shia leader Muqtada al-Sadr in Karbala, hospital sources have said. Witnesses said US forces had withdrawn from the city, 110km southwest of Baghdad, after the incursion early on Friday. Hospital sources said 15 other Iraqis were wounded in the clashes. The clashes took place in al-Saadia neighbourhood near al-Mukhayyam mosque in Karbala, Aljazeera's correspondent in Iraq reported. Other clashes also erupted in al-Shaabiya, al-Taalib, and al-Jamiya neighbourhoods, the correspondent added. US-led forces in Iraq have vowed to kill or capture al-Sadr and destroy his Mehdi Army militia. On Thursday US tanks swept into Najaf - another Shia holy city - and Karbala, pounding and killing fighters loyal to al-Sadr. **Policemen killed*** Meanwhile, a roadside bomb killed four Iraqi policemen and wounded one in the northern Iraq city of Mosul, police and hospital officials said. The bomb detonated as a patrol was passing through the al-Jadida district in the southern part of the city. Police said there was an exchange of gunfire with the attackers immediately after the attack, but no one was arrested. Mosul, about 400km north of Baghdad, has been relatively quiet in recent weeks, as fighters have focused attacks in and around Falluja, west of Baghdad, and in cities to the south of the country. **PHOTO CAPTION*** Iraqi child wounded during US attacks on Najaf. (Al-Jazeera)