Armed rebels have given Syria’s regime until midday today (0900 GMT) to observe Kofi Annan’s plan for ending bloodshed in Syria, warning they will take “courageous decisions” if the deadline is not met.

The ultimatum by the Free Syrian Army was followed by a demand from UN chief Ban Ki-moon that the regime implement Mr Annan’s six-point plan, which includes a ceasefire that should have taken effect on April 12 but has been violated daily.

A statement issued by the FSA command inside Syria said that if the regime “does not meet the deadline by Friday midday, the command... will no longer be tied by any commitment to the Annan plan... and our duty will be... to defend civilians.”

Parties to the conflict, which has seen more than 13,000 people killed since an anti-regime revolt erupted in March 2011, agreed to abide by the truce that was brokered by Mr Annan, the UN-Arab League’s peace envoy to Syria.

And despite the deployment of nearly 300 UN observers, the death toll has spiralled in recent weeks as regime forces assault opposition strongholds.

The FSA singled out last weekend’s massacre near the central town of Houla in which 108 people died, including 49 children and 34 women. Some were killed by artillery and tank fire but most were summarily executed, according to the UN High Commissioner for Human Rights.

“After the barbarous massacre of women and children at Houla ... we announce that there is no more justification for us to unilaterally respect the truce because (President Bashar al-Assad) has buried Annan’s plan,” the FSA said.

It added that it would announce in the coming days “a series of decisive and courageous decisions for the next phase” of their struggle against Mr Assad.

The rebels demanded that the regime adhere to all six points of the Annan plan: an end to armed violence, humanitarian access, an inclusive Syrian-led political process, the right to demonstrate, the release of political prisoners and access by the media to all parts of the country.

For his part, Mr Ban demanded at a forum in Istanbul that “the government of Syria act on its commitment to the Annan peace plan” and “act on its responsibilities to its people.”

Speaking of the Houla massacre, he said the bodies were counted by UN observers, “our eyes and ears of the international community.”

The observers are in Syria “so that perpetrators of crimes may be held accountable,” he said. “We are not there to play the role of passive observer to unspeakable atrocities.”

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