* Bomber blows herself among policemen
* U.S. military says 7 police officers among dead
* Second big bombing in a week in Iraq
By Dean Yates
BAGHDAD, June 22 Fifteen people were killed and 35 wounded when a female suicide bomber blew herself up among policemen having lunch north of Baghdad on Sunday, Iraqi police and hospital sources said.
The attack took place in Baquba, capital of multi-ethnic Diyala province, where Sunni Islamist al Qaeda militants have sought to create tension despite a succession of military offensives that have put the group on the back foot.
Police said the woman walked over to a group of policemen as they ate lunch at an outdoor restaurant then detonated explosives under her clothing. Several cars were set on fire.
Police and hospital sources said 15 people were killed in the attack, just outside a court house in Baquba, 65 km (40 miles) north of Baghdad.
The U.S. military said the blast killed 14 people including seven policemen.
At a hospital morgue, white sheets covered most of the dead. A man wailed over a body lying on a stretcher.
At least a dozen female suicide bombers have carried out attacks in the past six months, mostly in Diyala and Baghdad.
Security officials have blamed the bombings on al Qaeda, which they say has sought to recruit women because they can sometimes escape strict security checks on men.
Violence in Iraq has dropped to a four-year low, but Sunday's bombing was the second big attack in the past week.
U.S. forces have blamed a rogue Shi'ite militia group for a truck bomb that killed 63 people in Baghdad last Tuesday. That was the deadliest attack in Baghdad in more than three months.
U.S. officials accuse al Qaeda insurgents of carrying out scores of large-scale bombings, killing thousands of people in Iraq in the past few years.
A sustained military campaign against al Qaeda has pushed the group out of its traditional strongholds in Anbar province in the west and parts of Baghdad in the past year.
One region where al Qaeda forces regrouped was in the northern city of Mosul, described by the U.S. military as al Qaeda's last major urban stronghold.
Iraqi security officials say al Qaeda's network has been broken in Mosul following an offensive there.
OPERATIONS IN SOUTH
The Mosul operation was among several that Prime Minister Nuri al-Maliki has ordered in the past four months as he tries to impose order on areas once under the control of Shi'ite militias or Sunni Arab al Qaeda insurgents.
The most recent operation was launched on Thursday in the southern city of Amara, a stronghold of the Mehdi Army militia of anti-American Shi'ite cleric Moqtada al-Sadr.
Iraqi forces took control of Amara without a shot being fired after Sadr ordered his supporters not to resist.
Major-General Mohammed al-Askari, spokesman for the Iraqi Defence Ministry, said on Sunday a series of supporting operations had been launched in other southern provinces to catch militants who had escaped from Amara.
The presence of thousands of Iraqi soldiers in Amara, 300 km (185 miles) southeast of Baghdad, has made residents feel more secure.
"The situation is a lot different now. The militias and the Mehdi Army had controlled the city," said Ahmed Hattam, 34, the owner of an electronic appliance shop.
Louis Denkha, 32, a Christian who owns a clothes shop, said: "Now we see more women costumers ... Before we used to hide the women's lingerie, but now I display it inside my shop." (Additional reporting by Ahmed Rasheed, Aseel Kami, Aws Qusay and Tim Cocks in Baghdad and Aref Mohammed in Amara, Editing by Andrew Dobbie)