Two activist groups -- the Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees
-- say the factory is west of the city of Idlib. The LCC says at least 20 people were killed and many others wounded in the raid, while the Observatory said "tens were killed or wounded."
Both groups depend on a network of activists on the ground around the country.
President Bashar Assad's regime has been launching intense air raids on rebels in recent months, mostly in Idlib, the nearby province of Aleppo, Deir el-Zour to the east and suburbs of the capital Damascus.
The most recent air raids have killed hundreds of people, including eight children on Sunday in the village of Deir al-Asafir near the capital Damascus.
Olive oil is a main staple in Syria. Tens of thousands of tons are produced annually.
Fadi al-Yassin, an activist based in Idlib, told The Associated Press by telephone that dozens of people had gathered to have their olives pressed when the warplanes struck, causing a large number of casualties.
It was not immediately clear why the olive press was targeted. "It was a massacre carried out by the regime." said al-Yassin.
"Now is the season to press oil," said al-Yassin, noting that since many olive press factories are not functioning in the area because of the fighting in the region. A large number of people were at the one near the city of Idlib.
"Functioning olive press factories are packed with people these days," he said.
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The Observatory also reported heavy fighting on the southern edge of the strategic rebel-held town of Maaret al-Numan, captured from government troops last month.
The town is on the highway that links the capital, Damascus, with the northern city of Aleppo, Syria's largest, a commercial center that has been the scene of clashes between rebels and troops since July.
The Observatory and al-Yassin said air raids on Maaret al-Numan killed at least five rebels.
Syria's conflict started in March 2011 as an uprising against Assad's regime, but quickly morphed into a civil war that has since killed more than 40,000 people, according to activists.
Press; By BASSEM MROUE]
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