BAGHDAD, Iraq (CNN) -- Iraqis aligned with the Medhi Army have started trickling into police stations in Baghdad to exchange their weapons for coupons they can later use to get cash from the Iraqi government.

Rebels were expected to surrender thousands of medium and heavy weapons at various centers in the Sadr City area of the city under the control of police, the National Guard and City Council officials during a five-day amnesty, officials in Iraq's interim government said Monday.

Observers said the surrendering of rocket-propelled grenade launchers, mortars and machine guns was a sign an agreement between radical cleric Muqtada al-Sadr and the Iraqi government was being implemented as announced.

Iraqi Police Col. Fawzi Mahmoud said the weapons began arriving at 8 a.m. Monday at the al-Habibia police station on the outskirts of Sadr City.

"Until now, we have received a good number of weapons and Mehdi militia is still coming to this center to turn over its weapons," Col. Mahmoud said.

"The city is very quiet and the people have been very cooperative with the Iraqi police," he said.

When a weapon is turned in, the donor gets a receipt from police which can later be exchanged for cash from the Iraqi government.

Three police stations in Sadr City were ready to receive the weapons, another police official said.

The weapons surrender is intended to allow Iraqi security forces, backed by U.S. forces, to take control of the area where attacks on U.S. and Iraqi soldiers have been going on for weeks.

The sprawling slum of Sadr City is home to 2 million people, nearly 10 percent of Iraq's population.

In return for the weapons handover, the interim government said, there would be amnesty arrangements for people who "have not been involved in criminality."

Also, al-Sadr himself and his allies would be permitted to get involved in the country's nascent political culture.

Iraq's interim government and al-Sadr followers announced the deal Saturday.

Interim national security adviser Kasim Dawood called the plan a "breakthrough" deal and a "big achievement" toward consolidating national unity in Iraq.

Iraqi companies will be allowed to resume normal operations within Sadr City, but foreign companies will not be allowed in at this time, Sheikh Ali Smeisem said.

Meanwhile on Monday, a U.S. military convoy was attacked by a suicide car bomb in Mosul, northern Iraq, the U.S. military said.

Task Force Olympia spokeswoman Capt. Angela Bowans said there were military casualties, although the military was not yet saying how many or whether any troops were killed.

Hospital officials in Mosul said two Iraqi civilians were killed and 37 wounded, many of them critically. Dr. Raheem Ahmend of Mosul General Hospital said the hospital received the two killed and 30 wounded.

At Jumhuri hospital, Dr. Sahar Maher said seven wounded were being treated.

Bowans said a car was driven into the path of a moving military convoy at around 11 a.m. (0800 GMT) in southwestern Mosul. Military officials on the scene said the attack was followed by small arms fire.