BEIRUT - The European Union will impose harsher sanctions on Syria, a senior EU official said Wednesday, as Russia tried to broker talks between the vice-president and the opposition to calm violence. Activists reported at least 50 killed in the regime's siege of the restive city of Homs.

Russia, a close ally of Syria, and the West are pushing down starkly different paths in trying to deal with Syria's nearly 11 months of bloodshed. After blocking a Western and Arab attempt to bring U.N. pressure on President Bashar Assad to step down, Russia has launched a bid to show it can resolve the turmoil.

Moscow is calling for a combination of reforms by the regime and negotiations, without calling for Assad to go. Its provisions are so far finding no traction with the opposition, which dismisses promises of reform as empty gestures, refuses any negotiations while violence continues and says Assad's removal is the only option in the crisis.

Russian Prime Minister Vladimir Putin said outside forces should let Syrians settle their conflict "independently."

"We should not act like a bull in a china shop," Putin said, according to the ITAR-TASS news agency. "We have to give people a chance to make decisions about their destiny independently, to help, to give advice, to put limits somewhere so that the opposing sides would not have a chance to use arms, but not to interfere."

Russian Foreign Minister Sergey Lavrov, who met with Assad Tuesday in Damascus, told reporters in Moscow that the Syrian president delegated to his vice-president, Farouk al-Sharaa, responsibility for holding a dialogue with the opposition.

Lavrov blamed both Assad's regime and opposition forces for instigating the violence, which the U.N. says has killed well over 5,400 people.

"On both sides, there are people that aim at an armed confrontation, not a dialogue," Lavrov said.

Rebel soldiers are playing a bigger role in Syria's Arab-Spring inspired uprising, turning it into a more militarized conflict and hurtling the country ever more quickly toward a civil war.

In their meeting Tuesday, Assad said the government was ready to talk to the opposition and would co-operate with "any effort that boosts stability in Syria."

The regime's crackdown on dissent has left it almost completely isolated internationally and facing growing sanctions. The U.S. closed its embassy in Damascus on Monday and five European countries and six Arab Gulf nations have pulled their ambassadors out of Damascus over the past two days. Germany, whose envoy left Syria this month, said he would not be replaced.

In Brussels, a senior EU official said the 27-nation bloc will soon impose harsher sanctions against Syria as it seeks to weaken Assad's regime.

The official said the new measures may include bans on the import of Syrian phosphates, on commercial flights between Syria and Europe, and on financial transactions with the country's central bank. The European Union imports 40 per cent of Syria's phosphate exports.

The official, who spoke on condition of anonymity in keeping with EU rules, said some measures would be adopted at the EU foreign ministers meeting on Feb. 27. But he stressed the nature of the measures to be adopted remained unclear since the ministers are concerned over the impact on the Syrian public.

The U.N.'s top human rights official Navi Pillay called on nations to immediately act to stop the bloodshed, saying she was "appalled" by the Syrian regime's offensive against the central city of Homs, where activists say hundreds have been killed since Saturday.

She said the killings show an "extreme urgency for the international community to cut through the politics and take effective action to protect the Syrian population."

In New York, U.N. Secretary General Ban Ki-moon told reporters that the Arab League planned to send observers back to Syria and had asked the U.N. to consider a joint mission.

The U.N. chief provided no specifics, but the idea appears aimed at giving the regional group a boost after the league's earlier mission was pulled out of the country because of security concerns.

Ban called the continuing violence "unacceptable" and added: "I fear that the appalling brutality we are witnessing in Homs, with heavy weapons firing into civilian neighbourhoods, is a grim harbinger of worse to come."

On the ground, Syrian forces persisted with their assault on Homs, the country's third largest city, trying to put down what has been an epicenter of the uprising.

The Britain-based Syrian Observatory for Human Rights said at least 53 people were killed in Wednesday's shelling of the Homs neighbourhoods of Bayadah, Baba Amr, Khaldiyeh and Karm el-Zeytoun. The group also said that 23 homes were heavily damaged in Baba Amr alone.

Omar Shaker, an activist in Baba Amr, said his neighbourhood was under "very intense shelling" by tanks, mortars, artillery and heavy machine-guns. Shaker added that he counted five bodies Wednesday in his district. The death tolls, which the groups say they gather from activists on the ground, could not be independently confirmed. Syrian authorities keep tight control on the media.

"The situation is dire. We are short of food, water and medical aid. Doctors have collapsed after treating the wounded without rest for five days," Shaker said. "We want Lavrov to come and spend a night in Homs to see what we have been passing through."

The activist urged the international community to set up a safe passage so that women and children can leave volatile areas of Homs.

The head of the Observatory, Rami Abdul-Rahman, said the regime was trying "exhaust rebels in preparation for storming neighbourhoods."

The Observatory reported at least another eight civilians killed around the country.

The Assad regime says terrorists acting out a foreign conspiracy to destabilize the country are behind the uprising, not people seeking to transform the authoritarian regime.

Syria's state-run TV said gunmen fired mortar rounds at the oil refinery in Homs, one of two in Syria, setting two fuel tankers on fire. It also said attackers denoted a car bomb in the Homs neighbourhood of Bayadah, killing and wounding a number of civilians and troops.

Regime forces launched assaults on the village of Tseel in southern Daraa province on the Jordanian border, and the rebel-controlled mountain resort town of Zabadani, north of Damascus, the Observatory and another activist group, the Local Coordination Committees, reported.

Troops loyal to Assad also clashed with army defectors in the northwestern province of Idlib, bordering Turkey, the two groups said.