"The heavy machinegun fire and bullets were intense in areas of Latakia, Ramel, Masbah al-Shaab and Ain Tamra for more than three hours," said the Syrian Observatory for Human Rights.
Since Sunday, 30 civilians have been killed in Latakia in an offensive that according to rights activists saw use of gunboats by Syrian security forces for the first time since the start of pro-democracy revolts in mid-March.
The Syrian official news agency SANA has denied any maritime operation.
UN Relief and Works Agency (UNRWA), the agency for Palestinian refugees, reported that more than 5,000 refugees had fled the Ramel camp in southern Latakia under fire.
The military assault on Latakia has drawn sharp Arab and international condemnation, with Palestine Liberation Organisation secretary general Yasser Abed Rabbo saying it was "part of the crimes against humanity" targeting Palestinians and Syrians alike.
The Syrian daily Al-Watan said Tuesday Latakia was "under control" of the army.
"The situation (in Latakia) is under control, especially after the army arrested dozens of armed men during a complicated operation," it said.
"Armed men had set up barricades for laying mines to prevent the army from advancing," which "has led to residents fleeing the neighbourhoods," the daily added.
A resident of Latakia's Al-Slaibeh suburb, Yamam Alsham, told AFP via the Internet that the gunfire was relentless.
"We have become used to sleeping and waking up to the sound of gunfire every day. The shooting usually comes from security forces based on rooftops of the surrounding schools," she said.
Another resident of Latakia, who gave his name only as Tariq, said the security forces had cut off electricity and had severed landline connections.
"They're breaking into homes," he said. Checkpoints have been set up across the city and "all shops and bakeries have been closed."
According to Tariq, 15 army tanks had been stationed around Ramel and the security forces are "randomly sniping people."
The Palestinian refugees, he said, had gathered at a sports complex in the town.
He added that security force members were confiscating residents' identification cards at checkpoints and giving out shirts bearing President Bashar al-Assad's picture.
As he was speaking, several explosions rocked the neighbourhood and the sound of heavy gunfire rang out.
"They're firing ... bombs. It's raining bullets outside," he said.
"Sixteen cars with spotlights belonging to the security forces have just passed by. There's a man on the street and he seems to be covered with blood. They're taking him," he said.
An activist in the central city of Homs, meanwhile, said security forces opened fire on Tuesday in the suburbs of Bab Sibaa and Bayada, where they were also searching homes.
According to him, the death toll from the military operations in Homs and nearby Hula town had mounted to 12 since Monday.
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.
The first two weeks of August, since the beginning of Ramadan, 260 people, including 14 women and 31 children have been counted dead by coordinating committees of demonstrators.
US President Barack Obama said Assad has lost his legitimacy and his people "will be better off without him," the White House spokesman said.
"The Syrian people deserve a peaceful transition to democracy; they deserve a government that doesn't torture them, arrest them and kill them."
The State Department, however, said it was unable to confirm the reports of the Syrian navy shelling Latakia.
"We have been unable to confirm actually the use of naval assets," 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.
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.
Syria's neighbours Jordan and Turkey called for an immediate end to the violence.
Copyright AFP (Agence France-Presse), 2011