(Adds Maliki order, more violence)

BAGHDAD, Aug 30 (Reuters) - Iraqi security forces have arrested 72 gunmen following clashes in the city of Kerbala this week that forced hundreds of thousands of pilgrims to flee a religious festival, the Defence Ministry said on Thursday.

The ministry also said Prime Minister Nuri al-Maliki had ordered a mechanised Iraqi army unit to permanently protect two holy Shi'ite shrines that were lightly damaged by gunfire in the violence.

"The city of Kerbala is now witnessing stability and calm," the ministry said in a statement, adding a number of weapons had been confiscated during a search of homes across the southern city.

The gunbattles appeared to pit Iraq's two biggest Shi'ite groups against each other -- followers of cleric Moqtada al-Sadr and his Mehdi Army, and the rival Supreme Iraqi Islamic Council (SIIC), whose armed wing controls police in much of the south.

Maliki, who visited Kerbala on Wednesday, blamed "outlawed armed criminal gangs from the remnants of the buried Saddam regime" for the violence.

Up to 52 people were killed in day-long fighting around the Imam Hussein and the Imam Abbas shrines, two of the holiest in the world for Shi'ite Muslims.

In the wake of the chaos, Sadr suspended all armed activity by his Mehdi Army to remove rogue elements from the militia, several aides said on Wednesday. But violence by unidentified gunmen against SIIC offices has continued following a spate of attacks on Tuesday night.

Gunmen attacked two SIIC offices in Hashimiya, near the Shi'ite city of Hilla overnight, setting them both ablaze, police said. No one was hurt, police added.

An army source said gunmen also attacked a SIIC building overnight in the town of Haideriya, south of Kerbala.

Analysts have said the test of Sadr's six-month suspension order would be whether his fighters obeyed because it was no longer clear how much authority he exercised over the militia.

AlertNet news is provided by