The chief United Nations peacekeeper has condemned the Syrian government and rebel forces for their continued violation of a cease-fire agreement.

UN Under-Secretary-General for Peacekeeping Operations Herve Ladsous told reporters that both sides of the conflict were responsible for creating an atmosphere of appalling violence -- but he added that despite the bloodshed, the small UN presence was having a dampening effect.

Ladsous noted that the UN would also accelerate the deployment of peacekeepers to the war-torn country, with all 300 on the ground by the end of May.

We have 24 observers on the ground and I fully expect this number to increase rapidly over the next two weeks so that UNSMIS [United Nations Supervision Mission in Syria] will build up to full operational strength by the end of May, Ladsous said, according to Reuters.

The numbers are still small at the moment but they have had a visible impact We have 150 solid commitments (for observers) which are already being processed or already being deployed. We need more from member states .... (But) more pledges are coming in every day so I am confident we will do it.

The statement came as opposition group the Syrian Observatory for Human Rights said President Bashar al-Assad's forces had killed at least 43 people on Tuesday.

Mortar attacks on a village in Idlib province reportedly killed nine members of one family, including four women and two children, the BBC reported.

There were also reports of 12 government soldiers killed in the province of Deir al-Zour.

The UN estimates over 9,000 people have been killed during the 13-month rebellion, with opposition groups estimating the number may be as high as 11,000.