At least 25 people have been killed and many others injured after Syrian warships and tanks opened fire on the port city of Latakia, activists said.
A resident in al-Ramel, one of the neighbourhoods which came under attack on Sunday, said at least three gunboats were taking part in the offensive.
"Many homes have been destroyed and the shabiha have broken into shops and businesses," he said, referring to pro-government gangs.
Security forces also appeared to be intent on crushing dissent in the neighbourhood, which has seen large anti-government protests since the Syrian uprising began in mid-March.
The National Organisation for Human Rights in Syria (NOHRS) provided a list of 26 victims, including two Palestinian men from the Ramel refugee camp in southern Latakia.
A spokesman for the UN refugee agency UNRWA, Chris Gunness, said reports from the Ramel camp spoke of "fire from tanks which have encircled the area as well as fire from ships at sea".
"Poor communications make it impossible to confirm numbers of those killed and injured," Gunness said in a statement.
Rami Abdul Rahman, head of the UK-based Syrian Observatory for Human Rights, said one of the dead was a two-year-old girl who was in a car with her father when security forces at a checkpoint opened fire.
The assault on Latakia began on Saturday, when tanks and armoured personnel carriers rolled into al-Ramel amid intense gunfire. Five people were reportedly killed in the offensive.
State-run news agency SANA said troops were pursuing "gunmen using machine guns, hand grenades and bombs who have been terrorising residents in al-Ramel district".
The agency denied reports the area was being targeted from the sea. It quoted a health official in Latakia as saying two law enforcement officials were killed.
Ashraf al-Moqdad of the opposition Damascus Declaration comments on events in Latakia
Elsewhere in the country, NOHRS said two people had been killed in Homs, one in Hama and one in Idlib.
Around the capital, Damascus, "security forces entered Saqba and Hamriya in great numbers and launched a campaign of arrests," according to the Syrian Observatory for Human Rights.
Canada said on Saturday that it had expanded sanctions on Syria to protest against the government's brutal crackdown on demonstrations.
The new sanctions include travel bans on four officials and freezing the assets of the state-run Commercial Bank of Syria, and Syriatel, the country's largest mobile phone company.
The US imposed sanctions on the two firms earlier in the week, and has joined European allies in sanctioning top officials close to President Bashar al-Assad.
'Violence must end'
Canada's sanctions came after US President Barack Obama spoke with the leaders of Saudi Arabia and the UK and all three called for an immediate end to the Syrian government's crackdown on protests.
Obama and Saudi Arabia's King Abdullah "expressed their shared, deep concerns about the Syrian government's use of violence against its citizens," the White House said in a statement.
"They agreed that the Syrian regime's brutal campaign of violence against the Syrian people must end immediately, and to continue close consultations about the situation in the days ahead."
Similar language was used in a statement after a separate Obama conversation with David Cameron, the British prime minister.
Tens of thousands of people rallied in cities across the country on Friday in protest against the government and at least 17 people were reported killed.
The protests have grown dramatically over the past five months, driven in part by anger over the government's bloody crackdown in which rights groups say at least 2,000 civilians have been killed across the country.
The government has justified its crackdown by saying it is dealing with terrorist gangs and criminals who are fomenting unrest.
A Latakia resident speaking to Al Jazeera on Saturday rejected the government's claims. "There are no armed gangs here," he said. "We have been demonstrating peacefully for the last three months."
Syrian authorities have expelled most independent journalists since the five-month-old uprising against Assad began, making it difficult to verify reports from both sides.