Baghdad, May 10 (Reuters): US troops killed 35 members of rebel cleric Moqtada al-Sadr’s Mehdi Army militia in a series of clashes in Baghdad’s Sadr City suburb overnight, US spokesman Brigadier General Mark Kimmitt said today.

He said the two sides fought running battles in the alleyways of the impoverished neighbourhood before and after US forces destroyed Sadr’s office in the area. Mehdi Army commanders say US spokesmen exaggerate militia casualties.

The office was destroyed by a combination of gunfire from tanks, Bradley fighting vehicles and “perhaps helicopters”, he said. Local witnesses said earlier the office had been flattened by a bomb dropped from one of the US warplanes in the air at the time.

Earlier, a senior al-Sadr aide said the Shia cleric had ordered his militia to spread their battle against US troops across Iraq.

“We have now entered a second phase of resistance and our patience is over with the occupation forces,” said Qais al-Khazali, Sadr’s main lieutenant in Najaf, the holiest town in Iraq for the country’s Shia majority.

“Our policy now is to extend the state of resistance and to move it to all of Iraq because of the occupiers’ military escalation and crossing of all red lines in the holy cities of Karbala and Najaf,” he said.

“After every escalation there is more resistance, both qualitatively and in breadth and scope,” he added. “There will be volcanic eruptions.”

Several commanders in Sadr’s Mehdi Army have said they are bracing for a long and protracted conflict against US-led troops who have piled pressure on the militia in the last week.

US-led forces, spurred by increasingly public irritation among Shia elders at Sadr, who is around 30, have tightened their grip around Najaf while saying they have no intention of going anywhere near the holy shrines in the heart of the city.

They have also attacked Sadr offices in Baghdad, Karbala, Diwaniya and Amara south of the capital. But top Sadr aides say the full strength of the militia has so far not been displayed fully.

They also say the growing pressure from U.S.-led troops is pushing them closer to adopt more lethal tactics, including suicide bombings.

Khazali accused American forces of violating the sanctity of Najaf and the other holy Shi'ite shrine cities of nearby Kerbala and Kufa.

”They have shot 200 metres away from the tomb of Imam Hussein in Kerbala,” he said.“This is just one red line they have crossed.”

U.S. military spokesmen say dozens of Sadr's militiamen have been killed in Baghdad and around Najaf, Kufa and Kerbala in recent days.

On Sunday, there was fighting around the U.S. base on the outskirts of Najaf after militiamen fought tanks which moved to the warehouse area opposite the compound.

Several masked Mehdi Army fighters armed with AK-47 rifles and rocket launchers appeared defiant and unshaken by the overwhelming U.S. fire power they confront.

”For us no U.S. troops should enter the holy cities without ending up as corpses,” said one fighter calling himself Abu Ahmad.

Mehdi Army fighters say they are now waging a jihad (holy war) and are ready for martyrdom.