Air strikes on the Syrian city of Raqqa have killed at least 32 Islamic State (IS) militants and wounded 40 more, an activist group says.
The strikes on Sunday were believed to have been carried out by the US-led coalition, foreign sources states.
However, other activists suggested Russian jets had bombed the city and that civilians had been killed.
Raqqa is IS's de facto Syrian headquarters.
The UK joined the coalition bombing IS in Syria earlier this month following a vote in parliament. It was already targeting the group in Iraq.
France has also stepped up its attacks in Syria since deadly attacks in Paris in November claimed by the group.
On Friday, German lawmakers backed plans to back military action against the group in Syria.
Russia is also carrying out air strikes in Syria, although critics say it is mainly targeting rebel groups opposed to Syrian President Bashar al-Assad.