Syrian regime airstrikes killed three civilians and injured 15 others in an opposition-held area east of capital Damascus on Tuesday, according to a local civil defense official.

Regime warplanes carried out ten airstrikes on Ein Tarma suburb in the capital's eastern countryside, Alaa Mustafa told Anadolu Agency.

He said jet fighters launched numerous raids since Tuesday morning on opposition-held areas in Jobar, Qabound and Eastern Ghouta.

Syria has been locked in a vicious civil war since early 2011, when the regime of Bashar al-Assad cracked down on pro-democracy protests -- which erupted as part of the Arab Spring uprisings -- with unexpected ferocity.

Since then, more than a quarter-million people have been killed and more than 10 million displaced across the war-battered country, according to the United Nations.

The Syrian Center for Policy Research, however, put the death toll from the six-year conflict at more than 470,000 people.