At least 22 people died and 58 wounded in Basra, the hub of Iraq's oil industry, Time magazine reported.

Police reported at least five military vehicles were set on fire, The Washington Post reported.

Witnesses reported smoke plumes, the sounds of explosions and gunfire and deserted streets, Time said.

Although more than 4,000 British troops are stationed outside Basra, they have done little to curb the violence, The Post reported.

"We have a capacity to provide air and other specialist support if needed but at this time British involvement is minimal," a British Defense Ministry spokesman said.

As British troops withdrew from Basra, it has fallen under control of three Shiite militias -- Moqtada Sadr's Mehdi Army, the Iran-backed Badr Brigades and a group affiliated with the Fadila Party.

Iraqi Prime Minister Nouri al-Maliki and ministers for defense and the interior arrived in Basra Monday to oversee the operation.

Three Iraqi army brigades were deployed from Baghdad to Basra as backup for the operation and up to 15,000 troops could be involved, the BBC said.