Syrian troops have kept up their assault on the coastal city of Latakia, reportedly killing three people and forcing thousands of residents, including many Palestinian refugees, to flee their homes.
Residents told Al Jazeera that the army was using heavy machine guns and tanks, and had rounded up many people in a sports stadium as they attempted to escape the city.
Chris Gunness, a spokesman for the UN agency for Palestinian refugees, said 5,000 to 10,000 residents of a Palestinian refugee camp in the al-Ramel area of the city had been fleeing after the camp came under fire.
"As of 1pm (10:00 GMT), the army instructed all residents in southern and southeastern Latakia to evacuate", Al Jazeera's Nisreen El-Shamayleh, reporting from the Jordanian side of the Jordan-Syria border, said.
According to activists, most people started fleeing to the heart of the city and there Syrian troops arrested many of them.
"They transported them on buses to the sports city stadium and there they're being held captured, stripped of their IDs and mobile phones," El-Shamayleh said.
She said residents called the assault the "most atrocious attack" since protests against President Bashar al-Assad's government began five months ago.
The Syrian Revolution Co-ordinating Union, a grassroots activists' group, said three people were killed by security forces on Monday, bringing the total killed since Saturday to at least 31 civilians
The UK-based Syrian Observatory for Human Rights (SOHR) said one of the three was killed after troops opened fire as a group of fleeing residents approached a checkpoint in the Ein Tamra district of Latakia.
"People are trying to flee but they cannot leave Latakia because it is besieged. The best they can do is to move from one area to another within the city," a witness told Reuters.
UNRWA spokesman talks to Al Jazeera about
the situation at the Palestinian camp in Latakia.
Ahmet Davutoglu, the Turkish foreign minister, on Monday urged Syria to immediately end its deadly crackdown, threatening it with unspecified "steps" if it failed to do so.
Davutoglu said the bloodshed must end "immediately and without conditions or excuses."
"If the operations do not end, there would be nothing more to discuss about steps that would be taken," he said, without saying what that action could include.
Meanwhile, the White House said the US was working with other countries to pressure Assad to end the "outright murder of his own people."
"By his actions he [Assad] has demonstrated that he has lost legitimacy to lead," White House spokesman Jay Carney told reporters, adding that US President Barack Obama "has no doubt that Syria will be better off without him".
"The Syrian people deserve a peaceful transition to democracy; they deserve a government that doesn't torture them, arrest them and kill them. And we are looking, together with a broad array of international partners, to increase pressure on President Assad".
Germany called for more European Union sanctions against Syria and urged the UN Security Council to discuss the government crackdown there again.
'Listen to reason'
Meanwhile, neighbouring Jordan urged Syria to stop violence and start implementing reforms.
"Prime Minister Maaruf Bakhit today telephoned his Syrian counterpart Adel Safar and told him that violence must stop immediately," the state-run Petra news agency reported.
"Bakhit said Syria should listen to reason and start implementing reforms."
In-depth coverage of escalating violence across Syria
The government has justified its crackdown on the city by saying it is dealing with "terrorist" gangs.
On Sunday, official news agency SANA said troops were pursuing "gunmen using machine guns, hand grenades and bombs who have been terrorising residents in the al-Ramel district".
But a military source quoted by the agency on Monday denied reports that the army had been using gunboats in the offensive, saying ships seen off the coast were carrying out routine tasks of protecting the coast and preventing weapons smuggling.
Elsewhere in the country, troops backed by tanks reportedly entered several towns in the central province of Homs, a flashpoint of demonstrations.
"The community of Holeh is under siege ... The army is carrying out raids and arrests under the cover of heavy gunfire," the SOHR said. The group said a sniper had killed an elderly man.