Even for those who have become inured to the negative news coming from Syria, Friday's killing of 108 people in the village of Houla, near the city of Homs, should make them angry. It is only right that the United Nations Security Council should condemn the massacre "in the strongest possible terms" on Sunday.

UN observers confirmed civilians, including children, were shot at close range or stabbed and there were cases of severe physical abuse.

On Sunday, Syria denied the involvement of government troops in the Houla massacre, blaming "hundreds of heavily armed gunmen" who also attacked soldiers in the area.

Whoever was responsible must be found and held accountable. Such atrocities against civilians are beyond tolerance.

Continued violence is shattering the very basis of international efforts to find a peaceful solution to the crisis in Syria. All forces there should immediately cease violence in all forms, including the use of heavy weapons in population centers.

To uphold justice, the UN should continue to investigate the attacks and make public its findings at the earliest possible date. The international community should also exert more pressure on all forces in Syria to abide by the six-point plan, proposed by the UN special envoy Kofi Annan.

Anna's ceasefire plan, put into effect on April 12, highlights international efforts to find a political and peaceful solution to Syria's 14-month-old unrest. The UN has dispatched around 300 unarmed military observers and additional civilian staff to the unrest-torn country, tracking and documenting all violations to the ceasefire.

Nonetheless, clashes and killings are still being reported on a daily basis, and little has been achieved so far in trying to restore calm in the country. Even the UN peacekeepers themselves have become the target of violence several times since their arrival, reflecting the complicated and chaotic situation in the country.

In fact, the ceasefire has been shaky from the very beginning as mutual mistrust between the government and the opposition has overwhelmed endeavors to solve the crisis politically. Worse, terrorist groups, including members of al-Qaida in the region, have seized the opportunity to try and push Syria to the brink of a full-blown civil war.

Annan's ceasefire plan might be the last chance to solve the Syrian crisis in peace. All forces in Syria should honor their commitments and carry out the ceasefire to the letter. The top priority now is to prevent more civilian deaths.