DAMASCUS- Opposition fighters battled Syrian government forces in Damascus on Sunday in what residents described as the fiercest fighting yet inside the city limits of the capital, Reuters reported late on Sunday.
In turn, AFP reported that Syria's army blasted rebel strongholds in Damascus with mortars Sunday, sparking the 'most intense' fighting in the capital since the revolt erupted 16 months ago, a monitoring group said.
The army's offensive, aimed at driving rebels of the Free Syrian Army (FSA) out of Damascus, was launched soon after Syria's Foreign Ministry spokesman Jihad Maqdissi held a press conference to deny its troops had carried out a massacre in al-Treimseh village.
"The regular army fired mortar rounds into several suburbs" where FSA rebels are entrenched, said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
Numerous residents contacted by Reuters said they could hear loud explosions, persistent gunfire and sirens wailing, and described the fighting as the worst so far of the 17-month uprising against President Bashar al-Assad.
Thick black smoke was visible above the Damascus skyline in live Internet video links, Reuters added Sunday.
Press reports abroad indicated that fighting in the capital Damascus was heaviest in the Tadamon, Kafar Sousa, Nahr Aisha and Sidi Qadad neighborhoods, according to the Syrian Observatory for Human Rights.
"(It has) never been this intense," Abdel Rahman said.
"The security forces are attempting to take control of these neighborhoods but so far they have not succeeded," he added.
For its part, the Local Coordination Committees, which organise anti-regime protests in Syria, reported plumes of black smoke were billowing out of Tadamon Sunday night and that loud explosions had been heard in Nahr Aisha.
International press reported earlier that fighting has reached the outskirts of the capital in recent weeks, focusing on poorer areas where anger against the authorities is highest. The past week saw mortars fired inside the capital for what appeared to be the first time.
Also in Damascus, the UN Supervision Mission in Syria said Sunday a team of "specialised civilian and military experts" had visited Treimsa on Sunday to continue their investigation into the reports of the mass killing.
"The integrated patrol ... observed over 50 houses that were burned and/or destroyed. Pools of blood and brain matter were observed in a number of homes," UNSMIS spokesman Sausan Ghosheh said in a statement.
"On the basis of some of the destruction observed in the town and the witness accounts, the attack appears targeted at army defectors and activists," she added.
"The number of casualties is still unclear." Ghosheh said in a statement on Sunday.
International Press keeps telling that the Syrian government restricts access to the country by independent media, making verification of events difficult.