Syrian activists say France's first air strike on the Islamic State (IS) group in Syria has killed at least 30, including 12 child soldiers.

The British-based Syrian Observatory for Human Rights said some 20 militants were wounded in the September 27 strike on an IS camp in eastern Syria.

French President Francois Hollande has said six jets destroyed the camp in the province of Deir al-Zur and that more strikes could follow in the coming weeks.

French Defense Minister Jean-Yves Le Drian said the raid struck a "strategic hub" for militants travelling between Iraq and Syria.

He said France had evidence that foreign fighters were being trained in camps in Syria to carry out attacks in Europe.

France had previously limited its air strikes on IS to Iraq.

Based on reporting by AFP and dpa