A fuel tank exploded inside a clinic in the predominantly Kurdish northeastern Syrian town of Qamishli Sunday, killing at least 25 people, including children, state TV and activists said.

The Syrian TV report said the explosion also wounded 30.

Juan Mohammed, a Kurdish official in the nearby city of Hassakeh, said the explosion happened as the clinic was packed with children who were brought to receive polio vaccinations.

Mohammed said it appeared that a gas cylinder exploded inside the clinic in what led to an explosion of an oxygen cylinder that was nearby. He said that the two blasts led to a third explosion in the fuel tank killing 25 people including 12 staffers and some children.

The Britain-based Syrian Observatory for Human Rights said the fire killed 25 people adding that some of the wounded are in critical condition.

Also Sunday, Islamic State fighters captured the town of Souran Azaz and the nearby villages of Hasya and Bel in the northern province of Aleppo from moderate Syrian rebel groups. The villages are close to the Bab al-Salamah border crossing point with Turkey.

The Observatory said the fighting in the area killed 31 rebels and 22 ISIS members. ISIS has been fighting over territory with rebel groups in Aleppo since early last year.

In the northern city of Aleppo, rebels shelled a government-held neighborhood, killing 12 people, according to Syria's state news agency SANA. The Observatory said the shelling killed eight.

The shelling in Aleppo came a day after Syrian army airstrikes killed at least 70 people, most of them civilians, and wounded scores in attacks in Aleppo province.

More than 220,000 people have been killed in Syria since the start of the uprising against Syrian President Bashar Assad in March 2011.