An explosion ripped through an oil pipeline feeding a main refinery in the city of Homs on Monday and a plume of smoke was seen rising from the site, residents and activists said.

The explosion, the second in a week that hit the pipeline, which carries crude oil from the eastern Rumailan field, occurred in the district of Bab Amro, an opposition stronghold under heavy tank and mortar bombardment and rocket fire by President Bashar al-Assad's forces, they said.

Several pipelines in the province have been damaged by explosions in the past months.

The authorities and opponents of Assad, who has intensified a military crackdown to put down a revolt against his 11 year rule, have blamed each other for the explosions.

The official state news agency said an armed terrorist group bombed a gas pipeline on Sunday near the town of Talbiseh, 15 km (10 miles) north of Homs, that feeds a power station.

(Reporting by Khaled Yacoub Oweis, Amman newsroom; Editing by Alison Williams)