Two bombs have exploded near a checkpoint in western Iraqi city of Ramadi, killing at least 10 people, police and medics have said.

The first explosion killed a police officer and the second bomb went off five minutes later as police and bystanders gathered around the wreckage in the Sunni heartland of Anbar, which shares a border with Syria.

"We were on duty at a nearby checkpoint when the car exploded. We ran to work out what was going on, but before we reached the car it exploded again," said a policeman at the scene.

Police and hospital officials said at least 22 people were wounded in the attack on the checkpoint which was run by Sahwa, a Sunni group that joined forces with the US troops to fight al-Qaida during the Iraq War.

Since then, the group has been a target for Sunni fighters who consider its members traitors.

More than 1,000 people died in attacks across Iraq in May alone, making it the deadliest month since the worst of the sectarian bloodletting more than six years ago.

'Sidelined'

At the height of Iraq's insurgency in 2006-07, Anbar was in the grip of al-Qaeda's local affiliate, the Islamic State of Iraq, which has been regaining strength in the Sunni heartland in recent months.

Iraq's Sunni minority has felt sidelined since the US-led invasion in 2003 that toppled dictator Saddam Hussein and empowered the majority Shias.

Sunni Muslim fighters regularly target members of the security forces, heads of tribes and officials they see as supporters of the Shia-led government.

Sectarian tensions in Iraq have been amplified by the conflict in neighbouring Syria, where mostly Sunni rebels are fighting to overthrow President Bashar al-Assad, who is backed by Shia Iran.

Late on Thursday, bombs exploded in busy coffee shops and at other targets across Iraq, killing more than 20 people, police and medics said.