Syria has defied international calls to halt attacks on rebel enclaves, killing at least 89 people nationwide Saturday on the eve of a constitutional referendum that the opposition sees as a ploy designed by President Bashar al-Assad's regime.

Assad presented the revised charter, which allows for at least a theoretical opening of the country's political system, as an effort to placate critics and quell the 11-month uprising against his rule. However, the vote is unlikely to overshadow a new round of international condemnation and calls that Assad leave power.

The new charter would create a multiparty system in Syria, which has been ruled by the Assad family since Bashir's father Hafez seized power in a coup in 1963. Such change was unthinkable a year ago. However, after 11 months of bloodshed Assad's opponents say the referendum and other promises of reform are not enough and have called for a boycott of the vote.

Assad was roundly criticized Friday at a major international conference on the Syrian crisis in Tunisia, where American, European and Arab officials began planning a civilian peacekeeping mission to deploy after the regime falls. U.S. President Barack Obama said Friday of Assad's rule: "It is time for that regime to move on."

On Saturday, Turkish Foreign Minister Ahmet Davutoglu said Assad's crackdown belied promised reforms. "That kind of logic unfortunately renders any kind of reform meaningless," he said. "To fight on the one hand with your people and then to claim that there is reform is contradictory."

Still, Assad enjoys substantial support in many parts of the country. Some have benefited from his policies, others fear chaos or sectarian civil war if he falls.

Earlier Saturday, the Red Cross said it had failed to gain access to the besieged rebel stronghold of Baba Amr in the city of Homs but was able to carry out evacuations elsewhere in Syria, including other neighbourhoods of Homs.

The humanitarian group and its Syrian chapter are seeking safe passage for wounded and sick civilians in Baba Amr after managing to bring out 27 people on Friday. Hicham Hassan, spokesman for the International Committee of the Red Cross in Geneva, said talks with the Syrian government and opposition forces would continue Sunday.

On Friday, aid workers from the Red Cross and the Syrian Arab Red Crescent brought out seven wounded people and about 20 women and children in the first humanitarian operation since Syrian forces began bombarding Homs last month.

They transported the injured to nearby hospitals for treatment, state TV reported.

Activists say Syrian forces killed 107 people in Homs on Friday, including a woman and 14 children.

The UN estimated in January that 5,400 people have been killed in the conflict, which began last March. Hundreds more have died since, with activists saying the death toll is more than 7,300. Overall figures are impossible to confirm independently.

Representatives from about 70 countries, including Canada, have been meeting in Tunisia to discuss the crisis. On Friday, they called on Damascus to end the violence immediately, allow humanitarian access to areas under fire and permit the delivery of relief supplies.

"There was a vow from the Friends of Syria group to step up sanctions on Syria, including travel bans, asset freezes and reducing diplomatic links with Damascus, and there was an endorsement, too, for the main opposition umbrella group — the Syrian National Council — as a credible voice of opposition," Valitis reported.

U.S. Secretary of State Hillary Rodham Clinton again criticized Russia and China for refusing to attend this conference and for vetoing last month's UN Security Council resolution calling on al-Assad to step down.

On Saturday, Clinton warned of backsliding in the democratic transformations under way in the Middle East and North Africa and appealed for leaders and citizens to make good on the promise of reform offered by the Arab Spring and not abandon the democratic goals that sparked revolts throughout the region. Clinton called on Tunisians, particularly the young, to demand that their new leaders stay on the path of liberalization and openness.

"Protecting democracy is the duty of every citizen," Clinton said. "For young people here and across the region, this is a special responsibility. You were fearless on the frontlines of the revolution, enduring tear gas and beatings. It takes a different kind of courage to be guardians of your new democracy."

Tunisia was the first Arab nation to topple a longtime autocrat when its former president fled the country a year ago in the face of protests.

With files from the CBC