A powerful explosion has hit the heart of Damascus a day after Syria's prime minister narrowly escaped an assassination attempt in a heavily protected area of the city.

Residents said they heard a blast and saw thick, black smoke billowing from behind a group of buildings.

Gunfire was heard in the area immediately after the morning blast in the central district of Marjeh.

Earlier At least 15 opposition fighters were killed in a battle with Syrian government troops for a military helicopter base in the country's north.

The British-based Observatory for Human Rights said fighting between rebels and president Bashar Assad's troops was the Mannagh base in the province of Aleppo.

Rebels have repeatedly targeted Assad's air bases around the country in their two-year campaign to topple his regime. More than 70,000 people have been killed since the conflict started in March 2011.

State TV said 10 people had been killed in the latest Damascus explosion.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.