Two teenagers were killed on Wednesday when shelling hit a school sports ground where they were playing football in east Ukraine's rebel-held Donetsk, an AFP journalist and local officials said.

Two corpses lay covered by tarpaulin at the playing field close to the disputed airport in the war-torn city and witnesses said that at least four more people were wounded.

An elderly woman told AFP in tears that one of the victims was her 14-year-old grandson.

A statement from Donetsk city council said that both the victims were teenagers.

A spokeswoman for the firm that built the sports facility wrote on Facebook that those injured are aged 17 and 21, and one of them remains in a serious condition.

A representative for the charitable fund of Ukrainian oligarch Rinat Akhmetov, which paid for the school's reconstruction, told AFP that the incident happened while the youths were playing football.

Fierce fighting between government forces and pro-Russian rebels has raged on for control of the gutted remains of the strategic airport despite a nominal ceasefire signed in early September.

Over 4,000 people -- most of them civilians -- have been killed in the conflict in east Ukraine since April, the United Nations says.