Syrian rebel forces stepped up their attacks on parts of the capital Damascus Wednesday in some of the heaviest fighting inside the city in months.
Government forces responded with heavy shelling of inner districts of the capital and closed off the city's main Abbassid Square.
Amateur video shows what Syrian rebel fighters claim to be an attack on a government position in the Damascus district of Joubar.
Opposition activists say that the attack is part of a multi-pronged rebel attack on government forces near the capital's southern ring road.
Witnesses inside Damascus say that government forces have been shelling to try and repel the rebel attack. Sources inside the capital also say that the city's historic Abbassid Square was closed as fighting raged nearby.
The rebel Free Syrian Army issued a declaration calling Wednesday's assault "Operation Epic in the Capital of the Omayyids" to liberate Damascus. The statement listed six rebel brigades that were participating in the battle, including the al-Qaida-linked Jabhat al-Nusra.
Earlier, a government security compound was hit in the central city of Palmyra, where a pair of suicide car bombs exploded. Activists said the bombings targeted a military intelligence compound, killing at least 12 Syrian security personnel.
State media described the explosions differently, saying they went off in a residential area and killed several people.
Peter Harling of the International Crisis Group said that the rebel attack in Damascus may be an attempt to relieve pressure on the rebel-held suburb of Daraya, which has been under heavy government shelling and aerial bombardment for days.
He said despite reports that government forces have pulled back from certain areas of the capital under rebel pressure, it was unlikely that the government was about to collapse.
"The regime has rebuilt itself into a rather cohesive fighting force and I think this notion that it's losing ground is partly an illusion," Harling said. "I mean the regime has been losing ground consistently on the economic, political, moral levels, but I think militarily it's still extremely strong."
Harling added that the government has "massive human resources and military assets in the capital" and that its forces are "entrenched in a large and very defensible area in the heights of Damascus."
A recent call for a negotiated solution to the conflict by opposition leader Mouaz al-Khatib has hit resistance from various opposition groups. The opposition Syrian National Council said that it would meet soon to discuss the proposition.
Some information for this report was provided by AP, AFP and Reuters.