Activists say Syrian rebels have captured an oilfield in the country's east after three days of fierce fighting with government troops protecting the facility.

The Britain-based Syrian Observatory for Human Rights' chief Rami Abdul-Rahman says rebels overran the al-Ward oilfield in the province of Deir el-Zour near the border with Iraq on Sunday.

Omar Abu Leila, an activist in the area, says the field was still functioning until shortly before the rebels seized it.

Syria exported some 150,000 barrels of oil a day before European and U.S. imposed sanctions last year.

In 2010, Syria earned $4.4 billion by selling oil to EU countries alone. Oil was the main source of hard currency for the regime until the sanctions took effect.