BEIRUT — European officials said Wednesday they plan harsher economic sanctions on Syria, including a possible flight ban, as ally Russia pursued its own effort to resolve the crisis by trying to broker talks between the regime and opposition.
Amid the diplomacy, President Bashar Assad's regime pushed ahead with a relentless offensive on the city of Homs, the epicenter of the 11-month-old uprising.
Troops with mortars and heavy machine guns blasted at least four restive neighborhoods in the city, killing at least 53 people, activists said.
The assault reportedly has left hundreds dead the past five days.
Amnesty International warned that Homs is "turning into a major humanitarian crisis." It urged Russia to use its influence to stop the Syrian military from using heavy weapons in residential areas.
In online video taken by activists, the screech of rockets and the blasts of impacts can be heard, raising a cloud of smoke and dust from an apartment tower in Homs' Baba Amr district.
Fires blaze from a house and from the city's refinery hit in the fighting, and buildings across the urban landscape have gaping holes and crumbling walls from days of shelling.
Russia and the West had an acrimonious falling out over how to deal with Syria's crisis after Moscow and Beijing over the weekend blocked a Western-Arab attempt to bring U.N. pressure on Mr. Assad to step down.
Now each camp is pushing ahead on rival tracks.
Russia has taken a line close to Mr. Assad's position, saying reforms and dialogue can bring an end to the fighting, while avoiding calls for his departure.
Western and Arab nations have moved to isolate Mr. Assad while considering forming a coalition of nations to provide help to the opposition.
The U.S. says it is just a matter of time before Mr. Assad goes.
Turkey, a former ally of Mr. Assad that fell out with him over the bloodshed, is proposing an international conference in Istanbul or elsewhere in the Mideast to discuss creating an "international platform that would represent the conscience of humanity" to help Syrians, Foreign Minister Ahmet Davutoglu told a press conference.
He dismissed Mr. Assad's promises to Russia that he would carry out reforms, saying he had made and broken similar promises to Turkey. "We cannot allow the bloodshed of more of our brothers with these tactics to buy time," Mr. Davutoglu told NTV television.
The U.N.'s top human rights official, Navi Pillay, called for immediate action to stop the bloodshed, saying she was "appalled" by the regime's offensive in Homs.
The killings show an "extreme urgency for the international community to cut through the politics and take effective action to protect the Syrian population," she said.
Ms. Pillay's office estimated in early January that 5,400 people have been killed in Syria's upheaval since the uprising and the crackdown against it began in March. But it says it has been unable to update the estimate because of chaos on the ground. Hundreds have been reported killed since.
In Brussels, a senior European Union official said foreign ministers from the 27-nation bloc will decide on harsher sanctions against Syria aimed at weakening Mr. Assad when they meet Feb. 27.
The EU already has halted oil purchases from Syria, among other sanctions.