DIYARBAKIR, Turkey (Reuters) - Turkish Prime Minister Ahmet Davutoglu appealed for calm on Tuesday after crowds angered by renewed Kurdish militant violence attacked newspapers and offices of a pro-Kurdish political party.

The unrest took place after Kurdish militants killed 15 police officers in two bombings in eastern Turkish provinces.

More than 40 Turkish warplanes also hit Kurdistan Workers Party (PKK) targets overnight in northern Iraq, where the group has bases, in response to Sunday's killing of 16 soldiers near the Iraqi border -- the deadliest attack since a two-year-old ceasefire ended.

"It is unacceptable to damage media institutions, political party buildings and the property of our civilian citizens," Davutoglu said on Twitter, referring to the crowd violence.

"I invite all my citizens with hearts full of love for the country to calm, embrace one another, and to have confidence in the state."

Tuesday's bombing in Igdir province, which killed 14 police officers in a minibus, was the latest in a daily stream of attacks by the PKK on soldiers and police in eastern Turkey since fighting resumed in July.

A separate bomb attack in southeastern province Mardin killed one police officer and wounded three others.

President Tayyip Erdogan said the PKK had suffered "serious damage" inside and outside Turkey and was now on the defensive.

"The recent developments are a result of the ensuing panic. The losses inflicted on the organization by (Turkish military) operations can be expressed in the thousands," he said in a speech to academics at his palace in Ankara.

The renewed conflict, weeks before polls the ruling AK Party hopes will restore its majority, has shattered a peace process launched by Erdogan in 2012 in an attempt to end an insurgency that has killed more than 40,000 people over three decades.

It has also complicated Turkey's role in the U.S.-led fight against Islamic State. A Kurdish militia allied with the PKK has been battling Islamic State in northern Syria, backed by U.S. air strikes. But Turkey fears territorial gains by Syria's Kurds will fuel separatist sentiment among its own Kurdish population.

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Dozens of F-16 and F-4 jets took part in the air operation in northern Iraq, which began around 10 p.m. (1900 GMT) on Monday and continued for six hours.

They targeted PKK bases in Qandil, Basyan Avashin and Zap, and hit weapons and food stores as well as the militants' machinegun positions.

Military operations involving ground troops were continuing in a forested area right on the border, security sources said, but did not confirm Turkish media reports that special forces had crossed into Iraq in a "hot pursuit" maneuver - something they have done during past periods of intense conflict.

One of the sources said scores of PKK fighters were killed in the bombing raids. The PKK, which launched a separatist insurgency in 1984, is designated a terrorist organization by Turkey, the European Union and United States.

NATIONALIST ANGER

The Igdir attack came as police traveled in a minibus to a border gate linking Turkey to the autonomous Nakhchivan enclave, sandwiched between Armenia and Iran and controlled by Azerbaijan, the Dogan news agency reported.

Erdogan said on Sunday that some 2,000 PKK militants had been killed since the conflict resumed in July. Around 100 members of Turkish security forces have been killed, based on information from government officials and security sources.

The PKK attacks have triggered nationalist anger against Kurds. A crowd attacked the headquarters of pro-Kurdish opposition Peoples' Democratic Party's (HDP) in the capital Ankara on Tuesday night, the party said.

"There are hundreds in front of the building now, chanting slogans and throwing stones, breaking the windows of our building. Police are just watching," HDP lawmaker Garo Paylan told Reuters. Ankara police were not available for comment.

"What's being broken there is our hope of living together," Paylan said, and added that a small fire was put out by firefighters.

HDP said on Twitter that 126 of the party's buildings around the country were attacked on Monday.

Separately, the headquarters of Hurriyet newspaper in Istanbul was pelted with stones by a group, the daily said, less than 48 hours after a similar attack.

Crowds near the Mediterranean city of Mersin closed a highway and attacked buses traveling to largely Kurdish regions, breaking windows with rocks, newspapers reported.

About 2,000 people overran a state construction project in Erzurum province, angry with a group of ethnic Kurdish builders suspected of sympathizing with the PKK, the leftwing daily BirGun said. CNN Turk news channel said Kurdish seasonal farm laborers in the town of Beypazari near the capital Ankara barely escaped a group that attempted to lynch them.

Late on Tuesday, an HDP office and a nearby bookstore in central Anatolian province of Kirsehir was set on fire by an angry group chanting slogans in favor of killed soldiers and policemen. The bookstore belonged to an HDP official, media reports said.

(Reporting by Orhan Coskun, Gulsen Solaker and Ayla Jean Yackley; Writing by Daren Butler and Ece Toksabay; Editing by Nick Tattersall and Tom Heneghan)