At least 80 Syrian soldiers have been killed by rebels over the weekend, according to an activist group. The violence comes as Alex Thomson visits the villages blamed for the Houla massacre.
The Syrian Observatory for Human Rights (SOHR) said it had been told by rebels that 80 soldiers had been killed by them in a series of ambushes.
A Free Syrian Army spokesman said the rebels were no longer bound a truce.
“We have decided to end our commitment to this (ceasefire),” Major Sami al-Kurdi, told Reuters from Syria, adding that rebels had begun attacking government forces to “defend our people”.
SOHR said at least 19 soldiers, eight rebels and 19 civilians were killed in violence on Sunday.
Another 89 were killed on Saturday, including 57 soldiers, which the SOHR said was the largest number of fatalities the military had suffered in a single day since the start of the uprising against President Bashar al-Assad in March 2011.
SOHR head Sami Abdul Rahman said that there had been a sharp increase in the number of clashes between the army and rebels over the weekend.
“Troops are vulnerable to heavy losses because they are not trained for street battles and are therefore exposed to attacks,” he said.
“What exacerbates those losses is that the army is fighting locals of those towns and villages… who know the area inside and out and enjoy public support,” he added.
Mr Abdul Rahman said rebels had targeted military vehicles advancing on towns and villages.
Overnight, there were clashes in the Idlib province, as security forces used tanks, rocket launchers and artillery to bombard the towns of Kafr Nabal, Maarat al-Numan, Ariha and Rama, according to the main opposition coalition, the Syrian National Council.
Speaking in public on Sunday about the Houla massacre for the first time, President Assad said that even “monsters” would not have carried out such an act and it should prompt an end to bloodshed.
Chief Correspondent Alex Thomson goes in search of Houla's killers:
"I suppose a part of me feared hillside villages full of men with AK 47s and knives and a willingness to use both.
"In fact we found the usual and delightful warm hospitality of Syrians everywhere in the countryside. Valuable discussions over sweet Turkish coffee, the hookah pipe offered and several invitations to lunch.
Read more: In search of Houla's killers
Meanwhile, the European Council’s president said the EU and Russia must combine their efforts on Syria.
After a summit in St Petersburg with President Vladimir Putin, Herman Van Rompuy admitted they had different interpretations of the situation.
But both sides agreed the peace plan negotiated by the UN and Arab League envoy, Kofi Annan, was the best way to “break the cycle of violence in Syria, avoiding a civil war”, Mr Van Rompuy added.
“We need to combine our efforts in order for this to happen, and to find common messages on which we agree. We need to work towards an immediate stop of all forms of violence in Syria.”