The U.S. military says one its helicopters has crashed in southern Iraq, killing seven American soldiers.

The military says the Chinook (CH-47) aircraft experienced what it calls a "hard landing" early Thursday about 100 kilometers west of Basra.   It says the incident is under investigation.

The U.S. military says another two American soldiers died of non-combat related causes in Iraq on Wednesday.

Also Wednesday, a series of bombings in Baghdad killed 11 people and wounded more than 30 others.  In the deadliest attack, Iraqi officials said two car bombs went off in the west of the city, killing eight people.

Meanwhile, Iraqi Prime Minister Nouri al-Maliki said Wednesday that obstacles remain in negotiations with the United States on a long-term security pact.  He says one issue still in dispute is whether U.S. troops will continue to have immunity from Iraqi law.

Negotiators are trying to finalize a deal governing the U.S. military presence in Iraq after the end of this year, when a U.N. mandate for American troops expires. Any agreement would have to be ratified by Iraq's parliament.

Mr. Maliki says Washington has agreed to withdraw U.S. troops from Iraq in 2011.  U.S. officials have said no final agreement has been reached on a timetable for a troop pullout.

In another development, the U.S. military says it has detained an American soldier in Iraq on suspicion of shooting two fellow soldiers, both of whom were killed.  The incident happened Sunday in the Iraqi town of Tunnis.

Some information for this report was provided by AP and Reuters.