The U.S. forces decided to join the four-day fight in Basra between Shiite militias and Iraqi security forces, sending two aircrafts to bomb militia positions overnight.

The strikes were the first movements initiated by the U.S.-led coalition to support Iraqi army and police in the clashes that started on March 25. U.S. decided to join the fight after many followers of al-Sadr got involved in the clash.

On the third day of fighting, thousand of Shiites got out in the streets to protest against Iraqi security’s crackdown on Sadr’s militias, as new rocket attacks hit the area that hosts the U.S. Embassy.

The demonstrators chanted slogans against Prime Minister Nouri al-Maliki, who had ordered Iraqi security forces to suppress Sadr’s Mehdi Army.

“Maliki keep your hands off. People do not want you!” the protesters shouted.

The U.S. air strikes killed four militants in Baghdad’s Sadr City neighbourhood, which hosts the Mahdi militia of anti-American cleric al-Sadr. Iraqi officials insisted the dead were actually civilians.

The U.S.-led coalition in Basra was reduced to the minimum, after the British forces left the Iraqis responsibility for the area at the end of December, and, on this occasion, Iraqi government’s ability to control the situation was tested.

Prime Minister Nouri al-Maliki announced a deadline of April 8 for the Shiite militias to hand over medium and heavy weapons in Basra and receive money in return. The 72-hour deadline for an end to the violence also set by al-Maliki will expire tomorrow.

During a speech on Thursday, President Bush praised Iraq’s government for its crackdown on Shiite militias in Basra.

“This offensive builds on the security gains of the surge and demonstrates to the Iraqi people that their government is committed to protecting them,” he said, as reported by the New York Times.

“There’s a strong commitment by the central government of Iraq to say that no one is above the law.”