Seven children in the northern Syrian province of Aleppo and another four in Homs in the centre were among 17 civilians killed in air raids on Tuesday, a watchdog said.

The deaths in Homs come as troops pressed an offensive against remaining rebel areas there, while in Aleppo province, the raid comes exactly a year into the rebel takeover of the targeted town of Anadan.

Meanwhile, Islamist rebels downed a military helicopter with a ground-to-air missile near Damascus airport and a car bomb killed a leading Kurdish politician in the northeast, the Syrian Observatory for Human Rights said.

"The number of people killed in a regime air raid on Anadan has risen to seven children and three women," said the Syrian Observatory for Human Rights.

Activists and the Observatory said the strike targeted a mosque in Anadan, where the women and children were attending a religious studies class.

"The strike comes exactly a year on from the day rebels took control of Anadan," said the Observatory.

Earlier on Tuesday, a family of seven that had fled the army's recapture of Khaldiyeh in Homs city was also killed in a raid.

Four children were among the dead in the bombardment of Teir Maaleh village, the Britain-based Observatory said.

Elsewhere, Islamist rebels used a "sophisticated" ground-to-air missile to down the helicopter near Damascus International Airport, the watchdog added.

Rebels say they have received supplies of anti-aircraft weapons in recent weeks from friendly governments that are keen to help them counter the air superiority of President Bashar al-Assad's regime.

Outside Damascus, 10 rebels were killed in fighting in the Moadamiyet al-Sham area, over which the army is trying to restore control, the Observatory said.

Eissa Hasso, a leading member of the Democratic Union Party (PYD), Syria's biggest Kurdish group, was killed by a car bomb in the northeastern city of Qamishli, hard by the Turkish border.

"It is unclear whether he was assassinated by the regime, the Islamists or by a foreign intelligence agency," Observatory director Rami Abdel Rahman said.

Kurdish fighters have been fighting in the north and northeast with jihadists they have been trying to evict from Kurdish majority areas.

PYD leader Saleh Muslim was in Istanbul on Friday for talks with Turkish officials aimed at allaying concerns that the group -- which has close links with Turkey's Kurdistan Workers' Party -- is aiming for long-term autonomy inside Syria.

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