Syrian forces shelled opposition strongholds, killing at least 25 people, on Tuesday and a wounded British photographer was smuggled out of Homs into neighboring Lebanon.
France said the U.N. Security Council was starting work on a draft resolution on the violence in Syria and the need to gain humanitarian access to Homs and other embattled areas.
"We hope Russia and China will not oppose the proposed resolution," French Foreign Ministry spokesman Bernard Valero said. "Given the emergency, it's time that all the council members, without exception, put a stop to this barbarity."
Russia and China vetoed a draft resolution a month ago that would have demanded an end to the bloodshed and backed an Arab League call for Syrian President Bashar al-Assad to step down.
Activists said Assad sent units of an elite armored division, which is led by his brother Maher, into Homs overnight. Tanks with the words "Fourth Division Monsters" painted on them moved close to the besieged Baba Amro district.
British photographer Paul Conroy, of London's Sunday Times, was spirited safely out of Homs into Lebanon. "He is in good shape and in good spirits," the newspaper said.
Conroy had been among several foreign journalists trapped in Baba Amro, where Marie Colvin, a veteran war correspondent also with the Sunday Times, and French photographer Remi Ochlik were killed in a bombardment on February 22.
Some Syrian activists said Edith Bouvier, a freelance reporter working for French daily Le Figaro, who has a broken leg, had also escaped. But there was no immediate confirmation.
Valero, the French Foreign Ministry spokesman, said he could not confirm or deny the report. "We ask people to be extremely cautious with this kind of information," he added.
An activist with the campaign group Avaaz, which said it had arranged Conroy's escape, said Bouvier and two other Western journalists were believed to be still in Homs.
Protest Town Under Fire
In Hama province, security forces bombarded the town of Helfaya, a centre of protests in the uprising against Assad.
Activists said the 20 deaths of Sunni Muslim villagers there were among at least 100 killed in the province in the last two weeks in revenge for rebel Free Syrian Army attacks on security forces commanded by members of Assad's minority Alawite sect.
The reports could not be independently confirmed. Syrian authorities tightly restrict media access to the country.
Opposition groups say hundreds of civilians have been killed or wounded in the siege of Baba Amro and other rebellious districts in Homs, where terrified residents are enduring dire conditions, without proper supplies of water, food and medicine.
The Syrian military's latest bombardment of Baba Amro was the heaviest in a 24-day-old assault, activists said.
The Syrian Observatory for Human Rights said at least five people were killed in Baba Amro on Tuesday, a day after 84 were killed in Homs, out of an overall death toll of 122 civilians across Syria. The British-based group said 29 security force members had been killed in clashes with rebels on Monday.
Assad, projecting an aura of normality in a land ravaged by 11 months of conflict over his right to power, decreed that a new constitution was in force on Tuesday after officials said nearly 90 percent of voters had endorsed it in a referendum.
Opposition groups and Western leaders seeking Assad's removal denounced Sunday's vote as a charade that diverted attention from the violence in Homs and elsewhere.
In Geneva, the United Nations' main human rights body was set to condemn Syria for "brutal" use of heavy weapons on residential areas and persecuting opponents, its fourth such rebuke to Assad since the uprising began last March.
Turkey, Qatar, Kuwait and Saudi Arabia had requested the debate at the U.N. Human Rights Council, with Western backing.
An Arab diplomat said the 47-member forum, which has moral authority but no legal force, would back a resolution condemning Syria's "continued widespread and systematic violations," but that Russia, Cuba, Ecuador and possibly China might oppose it.
Of moves at the more powerful U.N. Security Council in New York, diplomats have indicated that Western powers may seek a compromise resolution focused on humanitarian relief that could avoid a new veto from Assad's allies in Moscow, or from Beijing.
Syrian Envoy Walks Out
Syria's U.N. ambassador in Geneva, Faysal Khabbaz Hamoui, stormed out of the session after calling on countries to stop "inciting sectarianism and providing arms" to Syrian rebels.
He said foreign sanctions were preventing Damascus from buying medicines and fuel. The European Union imposed additional punitive measures on Tuesday.
The outside world has proved powerless to halt the killing in Syria, where repression of initially peaceful protests has spawned an armed insurrection by army deserters and others.
French Foreign Minister Alain Juppe told the U.N. body on Monday it was time to refer Syria to the International Criminal Court and warned Assad he would face justice.
Foreign powers have argued over whether to arm Syrian rebels trying to resist Assad's forces, but there is little appetite in the West for any Libya-style military intervention.
Russia and China have used their vetoes to protect Syria from any action by the U.N. Security Council. Qatar joined Saudi Arabia on Monday in advocating arming the Syrian rebels.
Assad says he is battling a foreign conspiracy featuring "armed terrorist groups" and al Qaeda militants, while pressing ahead with political reforms toward greater democracy.
His opponents scorn his calls for dialogue as meaningless while Syrian security forces are violently repressing dissent.
The Syrian leader says the new constitution will lead to multi-party elections within three months.
The document drops a clause making Syria's Baath party the leader of state and society, allows political pluralism and limits a president to two seven-year terms.
But this restriction is not retroactive, implying that Assad, 46 and already in power since 2000, could serve two further terms after his current one expires in 2014.
The opposition dismisses the reforms on offer, saying that Assad, and his father who ruled for 30 years before him, have long paid only lip service to existing legal obligations.
A spokesman for China's Foreign Ministry said it hoped the referendum would "help push forward Syria's reform process, open political dialogue, and respond to the reasonable appeals of the Syrian people for protection of their interests."
(Additional reporting by Dominic Evans, Erika Solomon, Mariam Karouny, Catherine Bremer, Sui-Lee, Justyna Pawlak, Peter Griffiths, and Stephanie Nebehay)