Syria came under sharp Arab and international condemnation after rights activists said gunboats pounded Latakia port, forcing thousands of Palestinians to flee a refugee camp.
As activists reported new deaths at the camp, the Palestinians condemned Syria over the violence and the UN Relief and Works Agency (UNRWA) reported that more than 5,000 refugees had fled the Ramel camp in southern Latakia under fire.
The United States, however, said it was unable to confirm the reports of the Syrian navy shelling Latakia, in what would amount to a dramatic escalation in its bid to crush pro-democracy protests.
Palestine Liberation Organisation secretary general Yasser Abed Rabbo said the attack on Ramel was "part of the crimes against humanity" targeting Palestinians and Syrians alike.
Jordan, adding its voice to a chorus of Arab condemnation of the Syrian crackdown on dissent, urged Damascus to "immediately" stop the violence and "listen to reason," state-run Petra news agency reported.
US President Barack Obama said his Syrian counterpart Bashar al-Assad has lost his legitimacy and his people "will be better off without him," the White House spokesman said.
Assad "has to cease the systematic violence, mass arrests, and the outright murder of his own people," Jay Carney told reporters.
"The Syrian people deserve a peaceful transition to democracy; they deserve a government that doesn’t torture them, arrest them and kill them."
But as the uprising turned five months old on Monday, the violence continued unabated.
Troops and tanks clamped down on the flashpoint province of Homs, targeting the provincial town of Hula where snipers shot dead an elderly man, the Syrian Observatory for Human Rights reported.
The Britain-based group said four other people were killed in Latakia, including two as they tried to escape the Ramel district.
On Sunday, gunboats joined the pounding of Latakia that killed as many as 26 people, in the first attack from the sea since Syria's anti-regime revolt erupted on March 15, activists said.
The official SANA news agency denied the naval attack and said security forces were battling "armed gangs" in Latakia.
The United States also said Monday it could not confirm the naval attack.
"We have been unable to confirm actually the use of naval assets," US State Department spokeswoman Victoria Nuland told reporters, adding the "jury is still out" on whether or not Syrian warships opened fire.
She added there were "some inconsistencies" in the reporting on the alleged incident but did not elaborate.
"However, we are able to confirm that there is armour in the city and that there is firing on innocents again, in the pattern of carnage that you have seen in other places," she said.
Many residents were allowed to flee the worst-hit districts of Latakia at dawn, but soldiers opened fire at a checkpoint, killing a man, and a woman also died when her car was hit as she tried to leave Ramel, the Observatory said.
The watchdog said two other people were confirmed killed but that the death toll could rise because security forces hosed three other neighbourhoods in the city with heavy machine gun fire at sunset.
"There are reports of martyrs but we cannot confirm them," it said.
Chris Gunness, a spokesman for UNRWA which helps Palestinian refugees, said "between 5,000 and 10,000 people have fled" Ramel. "We need to get in there and find out what the hell is going on."
"We have called on the Syrian government to give us expeditious and unhindered access for humanitarian workers," Gunness added.
Syria's neighbours Jordan and Turkey called for an immediate end to the violence.
Syria has repeatedly said it is battling "armed gangs" -- a claim denied by rights groups who say the crackdown has killed 1,827 civilians since mid-March, while 416 security forces also died.
Advocacy group Human Rights Watch meanwhile on Tuesday said it had urged the European Union to freeze the assets of the Syrian National Oil Company, Syrian National Gas Company, and the Central Bank of Syria until Damascus "ends gross human rights abuses against its citizens."
"Syria’s authorities are still killing their own people despite multiple efforts by other countries, including former allies, to make them stop," said Lotte Leicht, EU director at the New York-based HRW.
"It’s time to show the government that Europeans won’t help to fund its repression."
Iran Tuesday warned Western states not to interfere in the "internal affair" of its regional Arab ally Syria.
"The events in Syria are its internal affair and there is no justification for any foreign intervention as it can only create many problems," foreign ministry spokesman Ramin Mehmanparast said during his weekly press briefing.
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