Activists: Syrian rebels detonate tunnels, kill 13

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Syrian activists say insurgents fighting to oust President Bashar Assad have detonated bomb-packed tunnels under buildings in the northern city of Aleppo, killing at least 13 pro-government troops.

The Britain-based Syrian Observatory for Human Rights says rebels detonated explosives Tuesday night in two tunnels, dug under the ancient quarter of the contested city of Aleppo. The Observatory says at least 13 soldiers and pro-government militiamen were killed. It says one bomb went off under a police station that likely housed troops.

There was no immediate claim of responsibility for the attack that comes amid reports of a surge in deadly attacks by the al-Qaida-breakaway Islamic State group targeting Assad's forces.

More than 2,000 Syrians -- almost half of them pro-government forces -- have been killed in just over two weeks.