Beirut, Aug 24 (AP) An explosion shook the base of an al-Qaida-linked group in northern Syria on Tuesday, killing and wounding dozens of fighters, opposition activists said.

It wasn't immediately clear what caused the explosion at the base of Hayat Tahrir al-Sham in the northwestern province of Idlib, the last major rebel stronghold in the country. HTS is the most powerful group in Syria's northwest.

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The Britain-based Syrian Observatory for Human Rights said the explosion near the village of Ram Hamadan was either an accident during training or a drone strike. It said 20 fighters were killed or wounded in the explosion.

Step news agency, an activist collective, said at least nine fighters were killed and others wounded in the mysterious blast. Step said it could have been caused when a mortar shell exploded during training.

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Syria's 10-year conflict has left about half a million people dead and half the country's prewar population of 23 million displaced, more than 5 million of them as refugees outside the country. (AP)

(The above story is verified and authored by Press Trust of India (PTI) staff. PTI, India’s premier news agency, employs more than 400 journalists and 500 stringers to cover almost every district and small town in India.. The views appearing in the above post do not reflect the opinions of LatestLY)