BEIRUT, Lebanon — In yet another escalation of its crackdown on dissent, the Syrian government unleashed navy vessels, tanks and a mix of soldiers, security forces and paramilitary fighters against the port city of Latakia on Sunday, killing at least 25 people, including three children, activists and residents said.

The attacks in Latakia marked the third weekend in a row that the government has defied international condemnations in its campaign to stanch a remarkably resilient uprising, which began in March. The attacks have stoked fresh outrage, in part because they have come during the Muslim holy month of Ramadan, traditionally a time of piety and festivity when observant Muslims fast from dawn to dusk.

For much of the summer, President Bashar al-Assad’s government seemed to lose momentum in the face of protests that brought out hundreds of thousands of demonstrators in Syria’s fourth and fifth-largest cities, Hama and Deir al-Zour. But this month, the government retook firm control first of Hama, then Deir al-Zour last weekend. Late on Saturday, it turned its attention to Latakia, which, like Syria as a whole, has a Sunni Muslim majority and an Alawite minority, the Muslim sect that is disproportionately represented in the country’s leadership.

The attacks grew in ferocity on Sunday, and activists and residents said for the first time that gunfire was coming from navy vessels anchored off the coast. As in Hama, activists said security forces fired anti-aircraft weapons at civilian buildings. In addition, the activists said, land-line telephones and Internet connections were cut off to some neighborhoods of Latakia, a city of 650,000 that serves as Syria’s main port.