DAMASCUS, May 29, 2012 (AFP) - Kofi Annan told President Bashar al-Assad of the world's "grave concern" about bloodshed in Syria, in a meeting Tuesday, as Western powers moved to expel Damascus' diplomats in protest at the Houla massacre.

The UN human rights agency estimated, prior to Annan's meeting with Assad, that fewer than 20 of the deaths of at least 108 people in the village of Taldu near the central town of Houla were caused by artillery and tank fire.

"According to local witnesses and survivors who have been interviewed, most of the rest of the victims in Taldu, one of the areas of Houla, were summarily executed in two separate incidents which local people are attributing to a shabiha paramilitary group," UNHCR spokesman Rupert Colville said.

In his meeting with Assad on the second day of his visit, Annan conveyed "the grave concern of the international community about the violence in Syria, including in particular the recent events in Houla," his office said.

"He conveyed in frank terms his view to President Assad that the six-point plan cannot succeed without bold steps to stop the violence and release detainees, and stressed the importance of full implementation of the plan."

Syria's government was upbeat about the talks.

"Positive & constructive meeting between Annan & President Assad this morning. Details discussed to push forward the plan & end violence," foreign ministry spokesman Jihad Makdissi said on Twitter.

The international community has reacted with horror over the deaths in Houla, where 49 children and 34 women were among those killed on Friday and Saturday, many of them shot dead at point-blank range.

France, Britain, and Australia all moved to expel Syrian diplomats in protest at the massacre, with Spain, Italy, Belgium and Canada all following suit.

"Canada and our partners are speaking loudly, with one voice, in saying these Syrian representatives are not welcome in our countries while their masters in Damascus continue to perpetrate their heinous and murderous acts," Canadian Foreign Affairs Minister John Baird said.

Australia's Foreign Minister Bob Carr said Syrian charge d'affaires Jawdat Ali and another unnamed official had 72 hours to leave the country.

"This is the most effective way we've got of sending a message of revulsion to the Syrian government," Carr said.

French President Francois Hollande announced the expulsion of the Syrian ambassador in response to the Houla killings, and said Paris would host a new meeting of the "Friends of Syria" group in July.

Syria's main opposition coalition welcomed the expulsions, and called for a UN Security Council resolution authorising the "use of force" to end the government's bloodshed.

After the expulsions and economic sanctions, the UN Security Council should "adopt a resolution under Chapter VII (of the UN Charter) allowing the use of necessary force in order to put a stop to the genocide and the murders committed by the regime's militias," the Syrian National Council said.

Assad's government has been using brutal force to crush an Arab Spring-inspired uprising, triggering a low-level insurgency by some regime opponents who have taken up arms.

The violence has killed more than 13,000 people, most of them civilians, according to the Syrian Observatory for Human Rights, a Britain-based watchdog.

And it has persisted despite the presence of more than 280 UN military observers as part of Annan's six-point blueprint aimed at ending the conflict.

At least 19 people were killed on Tuesday as fierce fighting was reported across Syria, including seven in central Homs province where last week's massacre occurred, said the Observatory.

The UN Security Council -- where Syrian allies Russia and China wield veto powers -- had on Sunday condemned the Damascus government's use of heavy artillery in the assault on Houla.

Annan told reporters in Damascus he was "personally shocked and horrified by the tragic incident in Houla," saying the UN body was right to condemn it.

He urged Damascus to take "bold steps" to signal it is serious in its intention to resolve the crisis peacefully.

"And this message of peace is not only for the government, but for everyone with a gun."

However, the Security Council's condemnation of the Syrian government's role in the massacre has done little to bring the international powers together to end the crisis.

Britain and France had proposed a text making an even stronger condemnation of the Assad government, but Russia defended its key Middle East ally and said both sides bore responsibility.

"Here we have a situation where both sides clearly had a hand in the fact that peaceful citizens were killed," said Foreign Minister Sergei Lavrov.

Assad's domestic opponents have already renewed their call to the international community to help Syrians defend themselves.

"The Syrian National Council calls (on) brothers and friends of the Syrian people to help before it's too late," the exiled group said in a statement.

The Free Syrian Army has warned that unless the international community takes concrete action it will no longer be bound by Annan's plan.

burs/sma/dv