By Leila Fadel and Yasseen Taha | McClatchy Newspapers

BAGHDAD — Iraqi Kurdish troops on Thursday encircled Turkish soldiers in northern Iraq and threatened to open fire in the most serious standoff between the two nation's forces since Turkey threatened late last year to go after guerrillas from the Kurdistan Workers Party sheltering in Iraq.

The standoff began when Turkish troops in tanks and armored vehicles left one of five bases they've had in Iraq since 1997 and moved to control two main roads in Dohuk province, Iraqi officials said.

Kurdish soldiers from the peshmerga militia, which is loyal to the Kurdish Regional Government, moved to stop them. For an hour and a half, the two sides faced off before the Turkish soldiers retreated to their base, which is about 27 miles northeast of the city of Dohuk. The peshmerga surrounded the base and remained there late Thursday.

The Turkish troop movement was accompanied by artillery and airstrikes that targeted mountain areas held by rebels from the Kurdistan Workers' Party, which is known by its initials as the PKK. A spokesman for the peshmerga, Jabar Yawar, said the shelling began at about 11 a.m. and continued past midnight. Two bridges were knocked out over the Great Zab River, he said.

"This is a matter of the sovereignty of Iraq and the unity of Iraq," said Falah Bakir, the head of the foreign relations department of the regional government. "We hope that there will be no clashes — the Kurdistan Regional Government has done enough to show our goodwill to Turkey."

Bakir said the regional government has tightened security at checkpoints, airports and hospitals to stop PKK movements, but that the Turkish military has continued its buildup. He called for the Iraqi central government and U.S. military to step in to stop what he called Turkey's "abnormal movements."

In Baghdad, Iraqi government officials held tense meetings with American civilian and military officials to stem the crisis in one of the only peaceful areas of Iraq.

"We have to do something," said a senior Iraqi official, who asked not to be identified because of the sensitivity of the issue. "We cannot keep quiet and keep digging our heads in the sand."

The growing tension between Turkey and Iraqi Kurdistan has wedged the United States between two allies. Turkey is a NATO member, and the Iraqi Kurds have been among the biggest supporters of the American presence in Iraq.

But the PKK, which has battled Turkey for decades for an autonomous Kurdish region in southern Turkey, also has broad support in northern Iraq, despite being labeled a terrorist organization by the United States.

There were no PKK casualties from Thursday's Turkish shelling, said Ahmed Dennis, a spokesman for the group.

Meanwhile, violence hit elsewhere in Iraq. In Diyala province, 24 bodies were found in two graves.

The Iraqi army discovered 15 men buried under a thin layer of dirt about 10 miles north of Baqouba, the province's capital, U.S. and Iraqi officials said. The corpses appeared to be about 10 days old. Each had been blindfolded, handcuffed and shot, Iraqi police said. Ten of the bodies were Iraqi soldiers.

The second grave also was near Baqouba; a police patrol uncovered the bodies of six men and three women.

Fighting between Shiite Muslim militias and the Iraqi army also broke out in Baqouba. An Iraqi army spokesman said the militias were affiliated with both Shiite cleric Muqtada al Sadr and the Islamic Supreme Council of Iraq, the country's most influential political party. It was unclear how many people had been killed in the fighting.

(Fadel reported from Iraq; Taha, a special correspondent, reported from Sulaimaniyah. Special Correspondent Ali al Basri contributed from Basra.)