BEIRUT, Lebanon — The first explosion tore into a busy street in Damascus. The second, which occurred minutes later as neighbors rushed to help those wounded in the first, may put an end, analysts said, to the effort by Palestinians in Syria to stay out of the country’s widening conflict.

At least 20 people were killed in the shelling on Thursday night, according to the United Nations. Witnesses recalled and an online video portrayed a horrific scene, with gnarled bodies in burning storefronts and women screaming in the streets.

But with responsibility for the attack a matter of intense dispute — the government blames rebels; the rebels blame the Syrian Army — its impact may reach beyond the carnage. Analysts said it could push Palestinian allegiances, already drifting from President Bashar al- Assad of Syria, fully into the rebel camp, greatly assisting the opposition’s struggle for recognition.

“The Palestinian cause is a central cause; it’s a builder of legitimacy and a basis for everything else,” said Joshua Landis, director of the Center for Middle East Studies at the University of Oklahoma. “The regime is clearly very protective of the issue, and the rebels are trying to establish a connection to it as well.”

The Assad government has long declared that it is the Palestinians’ grand protector, providing them with more rights than do Lebanon and supporting groups that have gone to war with Israel. In a nod to that history, most Palestinians have insisted on neutrality since the conflict in Syria began 17 months ago.

Trying to break that bond has been a primary goal of the opposition. And on Friday, Syrian activists urged Palestinian leaders to act.

“Palestinians in Syria already said that they were with Syrians, but politically and those who are out of Syria say that they don’t want to get involved,” said Susan Ahmad, a spokeswoman for the Revolution Leadership Council of Damascus. “Let them show the world how they don’t want to get involved after many of them were killed by Assad.”

Details surrounding the attack suggest it may not be that simple. The area where the shelling occurred, Yarmouk, is the largest Palestinian refugee camp in Syria with about 150,000 Palestinians, according to the United Nations, nearly a third of Syria’s Palestinian population. Even before the attack on Thursday, the neighborhood was becoming more politicized. Since the militant Palestinian group Hamas broke with the Assad government in February, residents said that various factional leaders had come under fire from young Palestinians who had marched or taken up arms against government troops.

“There is a huge gap between the factions’ position and the youth,” said Jafra, 25, who would give only her first name and said she had recently fled Yarmouk after a decade there. “The Yarmouk youth are supporters of the revolution.”

Other residents agreed, saying Yarmouk has become more divided. Founded in 1957 on the southern edge of Damascus, near railroad tracks, it is less a refugee camp than a working-class neighborhood with narrow streets, and gray apartment blocks. A roundabout called the Rotary of Return — surrounded before the unrest by tents for Palestinian factions — points to its identity.

But over the past few months as many as 300,000 refugees, rebels and activists have flooded the area there, according to local estimates. The Syrian military has mostly kept its distance, residents say, while the Free Syrian Army agreed not to have an armed presence.

Neutrality proved difficult to maintain, though. The neighborhood next door, Tadamon, is a rebel redoubt, and activists said fighters sometimes slipped into Yarmouk before or after skirmishes. A small anti-Assad demonstration in Yarmouk on July 13 turned violent when Syrian troops fired into the crowd. More recently, activists said, pro-government Palestinian factions began handing out weapons.

“We found it very provocative,” said Mahmoud Nassar, a Palestinian spokesman for the local opposition group. An all-out government assault followed this week. The shelling in Yarmouk occurred as the fighting continued, and the blasts appear to have hit near the office of a faction that was distributing weapons, the Popular Front for the Liberation of Palestine — General Command. A well-placed opposition activist who declined to be identified publicly because of political considerations said the bombings might have been the work of rebels who had aimed for that office but missed.

Other activists blamed the government although they acknowledged that they wanted to draw the Palestinians into the conflict.

That has yet to fully happen. On Friday, the Palestinian Leadership Organization issued a statement condemning the Yarmouk attack, without assigning blame. Hamas also denounced “the heinous crime” and “all attempts to drag the Palestinians into Syria’s painful events.”

But in a sign of the Assad government’s concern, it issued a rare statement blaming “terrorist mercenaries,” a term it uses for insurgents, for the attack. Some residents said most people in Yarmouk would consider Mr. Assad responsible, directly or indirectly.

If government troops did shell Yarmouk, it would represent a significant shift. Syria’s support for the Palestinians is a core element of its bond with Iran and Lebanese groups like Hezbollah, and since the conflict began 17 months ago, Mr. Assad has been careful not to direct the full force of his military against Palestinians. But analysts said government troops may have misfired or simply become fed up with the support many rebels have enjoyed in Yarmouk.

Momentum may be shifting, said Hilal Khashan, a political science professor at the American University of Beirut. Rebel brigades have held tight in Aleppo through nearly two weeks of fighting, which continued on Friday. The government is also being forced to fight on several fronts in addition to Aleppo. Though it is impossible to independently verify, rebels reported fighting on Friday in Aleppo, Damascus, Homs, Hama, Deir al-Zour and Dara’a.

“The regime feels isolated, and they are known for vindictiveness,” Dr. Khashan said. “What they did in Yarmouk was an example of what they are capable of.”

Hwaida Saad contributed reporting from Beirut, and an employee of The New York Times from Aleppo, Syria. (Copyright 2012 The New York Times Company 08/04/12)