The Syrian government blamed “terrorists” Thursday for a massive explosion in the central city of Hama that killed at least 16 people as Syria's tenuous cease-fire continues to unravel amid more violence and a rising death toll.

Both government and rebels traded blame over the blast that caused a huge fireball in a residential neighborhood on Wednesday. The state-run news agency said terrorists were setting up an explosive device when it detonated in the neighborhood.

Anti-government activists, however, blamed security forces for causing the incident, which they say was part of violence that claimed at least 27 lives across the country on Wednesday.

On Thursday, the Syrian Revolution General Commission says seven people were killed in anti-government related violence. It says most of the deaths resulted from government shelling in the eastern region of Deir el-Zour.

The opposition Syrian National Council called for an emergency U.N. Security Council meeting that would focus on protecting civilians in Syria. The group cited escalating attacks in Hama and other cities as reasons for the request.

The violence continues even though a United Nations truce-monitoring team is returning to areas including the Damascus suburb of Douma on Thursday.

After a visit Wednesday, observer mission spokesman Neeraj Singh says violence in the flashpoint city of Douma needs to “de-escalate.”

“In this process we have a role of de-escalating the situation. We do that — and we did that yesterday in Douma — by maintaining our presence on the ground, patrolling the area for a good number of hours, through our liaison activities.”

Over the coming months, the U.N. observer mission will expand from its current level of about a dozen monitors to about 300.

Carnegie Middle East Center Director Paul Salem tells VOA Syria's continued violence will make it clear to observers that the cease-fire brokered by envoy Kofi Annan is not being implemented.

“I think it will be clear to the monitors very soon that this cease-fire is certainly not holding in a significant and final way.”

Salem says the presence of more U.N. monitors may not be enough to curb violence.

“Syria is a very large country. The violence has moved from one location to another. It will be a challenge for the monitors to try to be in all places all the time. It's also the case, I think, that the government will claim that when violence does erupt, they will claim that it started from the rebels and they are just responding.”

The United Nations estimates that more than 9,000 people have been killed in Syria's crackdown on the uprising, while activist groups put the death toll at more than 11,000.