A suicide car bomber has killed four U.S. soldiers outside Baghdad, as coalition forces continue their offensive against insurgents near Syria's border.

Military officials said the four soldiers were killed in a suicide attack on a checkpoint south of the Iraqi capital Monday.

Meanwhile, coalition forces battled insurgents for a third day in the Iraqi border town of Husaybah, where officials say one Marine and 36 insurgents have died.

Officials say coalition forces have encountered frequent attacks by snipers and discovered homemade bombs in the area.

There are no reports of civilian casualties in the operation aimed at stopping the flow of weapons and foreign fighters from Syria.

Near Baghdad, separate attacks killed 13 people, including six Iraqi police officers.

Some information for this report provided by AP, AFP.