* Police station, market hit in two bomb attacks
* Wave of violence in ethnically mixed northern Iraq
(Adds details, byline, updates number of wounded)
By Sabah al-Bazee
SHIRQAT, Iraq, Aug 29 (Reuters) - Two bomb attacks in volatile parts of northern Iraq killed at least 15 people on Saturday and wounded 37, police said, interrupting a relatively peaceful start to the Ramadan fast.
In one attack, a suicide bomber drove a car packed with explosives and rockets into the main gate of a police station on the outskirts of Shirqat, a town 300 km (190 miles) north of Baghdad, at about 8 a.m. (0500 GMT), police said.
Police opened fire to stop him but he detonated the load, killing at least nine people and wounding 17.
Four of those killed in the attack were police. The blast also damaged more than a dozen shops, two dozen cars and left a 2-metre-wide (7-foot) crater in the road, a Reuters reporter saw.
Glaring at the wreckage, an old man cried out: "Shame on them! Why must they do something like this during Ramadan?"
Ahmed Mehdi, 35, said he lost a cousin in the blast.
"What did these innocent people do to deserve to be killed like this?" he said. "Whoever did this does not fear God. Most of the people killed here were civilians."
Later, a truck bomb parked beside a market killed six people and wounded 20 in the town of Sinjar, 390 km (240 miles) northwest of Baghdad. Sinjar is mostly inhabited by Yazidis, members of a pre-Islamic Kurdish sect.
At least 21 people were killed in two suicide attacks in Sinjar earlier this month, part of a wave of violence that has hit ethnically and religiously mixed northern Nineveh province where tension is high between majority Arabs, ethnic Kurds and other minorities.
Iraq is struggling to heal the scars of years of sectarian slaughter and an insurgency triggered by the 2003 U.S.-led invasion that rendered the country practically ungovernable.
But a rash of violence in the past two months has raised doubts about whether Iraq’s security gains over the past two years will hold up, including truck bomb attacks that killed almost 100 people at two government ministries on Aug. 19.
The Shi’ite Muslim-led government, looking towards a general election in January, wants to show Iraqis that it is on top of the security situation as U.S. troops prepare to withdraw gradually by the end of 2011. (Additional reporting by Jamal al-Badrani in Mosul; writing by Missy Ryan and Tim Cocks; editing by Robin Pomeroy)