By Khaled Yacoub Oweis
AMMAN, Feb 28 (Reuters) - Syrian forces shelled an opposition stronghold in Hama province, killing 20 people, on Tuesday and hit rebel-held parts of Homs, activists said, as two wounded foreign journalists trapped in the city were reported to have been smuggled safely to Lebanon.
President Bashar al-Assad sent units of an elite armoured division, which is led by his brother Maher, into Homs overnight, activists said. Tanks with the words "Fourth Division Monsters" painted on them moved close to the besieged Baba Amro district.
French journalist Edith Bouvier and British photographer Paul Conroy, both wounded last week in an attack in Baba Amro, were now safe in Lebanon, a diplomat and opposition sources said. It was not clear how they escaped.
In Hama province, security forces bombarded the town of Helfaya, a hotbed 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.
Syrian forces on Tuesday launched the heaviest bombardment in their three-week assault on Baba Amro, activists said.
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.
Assad's government had "broken all the limits of barbarism". French Foreign Minister Alain Juppe said.
"And when I see the Syrian president paraded around this voting station in Damascus for this phony referendum, it makes you deeply indignant," he told RTL radio.
Juppe said he felt "immensely frustrated" at difficulties in obtaining security guarantees to enable wounded civilians and Western journalists to be evacuated from Homs.
American reporter Marie Colvin and French photographer Remi Ochlik were killed in Baba Amro on Feb. 22 in a strike on a house in which Conroy and Bouvier were wounded.
The Syrian Arab Red Crescent did manage to evacuate three people from Baba Amro on Monday, but not the foreign reporters, the International Committee of the Red Cross (ICRC) said.
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.
"As long as we have not halted the massacres, we are impotent, but we are not inactive," Juppe said.
He told the U.N. Human Rights Council in Geneva on Monday it was time to refer Syria to the International Criminal Court and warned Assad he would be brought to 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, where Western and Arab powers had sought backing for an Arab League transition plan under which Assad would voluntarily relinquish office.
Qatar joined Saudi Arabia on Monday in advocating arming the Syrian rebels. "We should do whatever is necessary to help them, including giving them weapons to defend themselves," Qatari Prime Minister Sheikh Hamad bin Jassim al-Thani said in Oslo.
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. (Additional reporting by Dominic Evans, Erika Solomon and Mariam Karouny in Beirut; Writing by Alistair Lyon, Editing by Rosalind Russell)