An oil pipeline has been attacked and left on fire in the central Syrian city of Homs, and regime troops have stormed several residential neighbourhoods in the nearby city of Hama, activists said.
The Local Co-ordination Committees and the Britain-based Syrian Observatory for Human Rights said the Homs pipeline was in the rebel-held neighbourhood of Baba Amr, which has been shelled by regime troops for the past 12 days.
The Observatory and the LCC also said that government forces launched a new operation today in another flashpoint city, Hama, after telephone, mobile phone and internet connections were cut.
"Loud explosions were heard in the neighbourhoods" of Hama, the Observatory said in a statement.
Video by Homs activists broadcast on social networking sites showed thick black smoke billowing from what appeared to be a residential area.
Homs is home to one of Syria's two oil refineries. It has also been one of the cities hardest hit by president Bashar Assad's crackdown on the popular uprising that began in March.
The uprising started out as mostly peaceful protests against Assad's authoritarian rule but has become more militarised in the face of the regime's brutal crackdown.
UN human rights chief Navi Pillay told the General Assembly this week that more than 5,400 people were killed last year alone, and that the number of dead and injured continues to rise daily.
Syria's oil and gas pipelines have been attacked before during the 11-month uprising.
The state-run news agency Sana blamed "armed terrorists" for the attack on the pipeline. It said the pipeline feeds the tankers in the Damascus suburb of Adra, which contribute in supplying fuel to the capital and southern regions.
Assad's regime has long blamed "terrorists" and foreign conspiracies for the country's crisis, not protesters seeking democratic reforms. The revolt began with peaceful calls for democratic change, but has been morphing into a bloody, armed insurgency.
Also today, the Observatory reported that government troops were conducting raids in the Damascus suburb of Barzeh, detaining scores of people, as well as in the village of Ashaara in the eastern province of Deir el-Zour.