BEIRUT — A powerful Kurdish militia said Tuesday it is mobilizing against al-Qaida-linked rebels in northeastern Syria after a Kurdish opposition leader was killed in the area.

The fight between the Kurds and the extremists has become a war within a war in Syria's oil-rich region. Clashes between Kurdish gunmen and members of al-Qaida-linked Jabhat al-Nusra and the Islamic State of Iraq and the Levant over the past weeks left dozens of gunmen dead from both sides.

The fighting claimed a prominent casualty Tuesday, as a car bomb killed Kurdish leader Issa Hisso, said the Kurdish Democratic Union Party, the most powerful faction of the ethnic group in the region.

"We condemn this ugly criminal act and we promise the martyr and his comrades that we will stand idle," the party said in a statement.

Hisso opposed and was imprisoned in the past by President Bashar Assad's regime. He also spoke out against radical Islamic groups, including the al-Qaida-linked Jabhat al-Nusra and the Islamic State of Iraq and the Levant. Both groups have gained influence in the opposition after leading several battles.

Though no group claimed responsibility Tuesday for Hisso's slaying, suspicion fell on the al-Qaida-linked organizations. Nawaf Khalil, a spokesman for the party, said fighters hoped to clear the groups out of Kurdish areas.

"The military units have declared mobilization," he said. "The jihadi forces or forces of darkness have been attacking Kurdish areas so it is normal that there be military and political mobilization.

Kurdish gunmen and al-Qaida-linked groups already have fought sporadic battles over the past months.

Kurds, the largest ethnic minority in Syria, make up more than 10 percent of the country's 23 million people. Their loyalties in the conflict are split, though Kurds in opposition areas have carved out a once unthinkable degree of independence in their areas. They've creating their own police forces, issuing their own license plates and exuberantly going public with their language and culture.

Meanwhile Tuesday, the Britain-based Syrian Observatory for Human Rights said a car bomb went off in the town of Maabadeh in Hassakeh province. It said the blast wounded some people and was followed by deployment of Kurdish gunmen in the area.

More than 100,000 people have been killed in the conflict and millions have been driven out of their homes, seeking shelter in safer areas of the country or in the neighboring Iraq, Jordan, Lebanon and Turkey.

Activists also reported that an Italian Jesuit priest, Father Paolo Dall'Oglio, has gone missing while on a trip to the rebel-held northeastern city of Raqqa. Dall'Oglio is an Assad opponent who was expelled last year from Syria, where he had lived for 30 years.

He reportedly went in to Raqqa to meet with al-Qaida-linked militants there. On Saturday, he posted on his Facebook page in Arabic that he felt happy to be in a "beautiful, free" city. Videos posted online showed him surrounded by a boisterous crowd in Raqqa this past weekend, giving a speech.

The Observatory said Dall-Oglio had told an activist in the city Monday that he was going to meet with the al-Qaida-linked Islamic State of Iraq and the Levant. It was not clear whether he was still on his mission or had been abducted.

Earlier in the day, mortar attacks and air raids in two major cities in Syria killed at least 17 people, activists and government officials said.

The deadliest attack struck the central city of Homs, which has been an opposition stronghold since the beginning of the two-year conflict and is now the target of a withering offensive by President Bashar Assad's forces.

Three mortars slammed into a government-held district of Dablan before dawn Tuesday, killing 10 people and wounding 26 others, a government official. He said many living in the neighborhood fled there to escape fighting elsewhere in Homs. The official spoke on condition of anonymity in line with regulations for civil servants.

The Observatory said 11 people – including a child – were killed. It cited hospital officials and also said attack happened late Monday close to midnight.

Homs has been the center of protests against Assad's rule since the Syrian revolt started in March 2011. In recent weeks, the city has been the scene of fierce fighting between Assad's troops and rebels fighting to topple his regime. On Monday, government troops captured Homs' strategic area of Khaldiyeh after a monthlong battle, bringing Assad's regime closer to its goal of capturing all of Syria's third largest city.

In northern Syria, regime warplanes hit the town of Andan, killing seven people, including five children, the Observatory said.

___

Associated Press writers Albert Aji in Damascus, Syria, and Barbara Surk in Beirut contributed to this report.

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