The United Nations Commission of Inquiry on Syria says both pro- and anti-government forces have become increasingly violent and reckless with human life as the increasingly sectarian conflict draws to the close of its second year.

"The dynamics of the conflict have become increasingly complex," a U.N. panel reported on Feb. 18 about the civil war waging in Syria.

"The war has become colored by sectarianism, permeated by opportunistic criminality and aggravated by the presence of foreign fighters and extremist groups."

One of the U.N. human rights investigators recommended the U.N. Security Council should refer Syria to the International Criminal Court in The Hague to prosecute those responsible for war crimes and other abuses.

Speaking at the U.N. Human Rights Council in Geneva on Monday, Carla del Ponte said, "We are pressuring the international community to act because it's time to act."

"The depth of the Syrian tragedy is poignantly reflected in the accounts of its victims. Their harrowing experiences of survival detail grave human rights violations, war crimes and crimes against humanity," says the report.

The war is tearing apart the country's complex social fabric. It is jeopardizing future generations and undermining regional peace and security, it says.

"The issue of accountability for those responsible for international crimes deserves to be raised in a more robust manner to counter the pervasive sense of impunity in the country," the panelists say in the 131-page report.

The report notes, "The lack of access to the Syrian Arab Republic has significantly hampered investigations in to the conduct of hostilities by anti-government armed groups."

The report says government forces and anti-government armed groups have perpetrated massacres of civilians and "hors de combat fighters", soldiers incapable of fighting.

Across Syria, during house searches and at checkpoints, government forces and affiliated militias have arbitrarily arrested individuals.

It reports murder, torture, rape, enforced disappearance and other inhumane acts have taken place at centers run by the pro-government forces.

"Committed as part of a widespread and systematic attack, they may constitute crimes against humanity," says the report.

It notes that some minority communities, notably Alawites, who form a strong presence in the security forces of Syrian President Bashar Hafez al-Assad and Christians, have formed armed self-defense groups.

These are "supposedly to protect their neighborhoods from anti-government fighters by establishing checkpoints around their areas."

Known in some area as Popular Committees the U.N. panelists said they were said to be armed and equipped by the government and have participated alongside government forces in military operations in Damascus and Homs.

The report emphasizes the urgent need for parties to the conflict to commit to a political settlement to end the violence.

It says that in the last six months the conflict became "increasingly violent and complex" and that efforts to achieve a political settlement failed.

"In supporting various parties in the Syrian Arab Republic, regional and international actors hampered the prospects of a negotiated settlement owing to their divergent interests. The position of key international actors remains unchanged."

Prior to the conflict, Syria hosted different groups of refugees, including 500,000 Palestinians and 150,000 Iraqis.

The report said the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) estimates that 400,000 Palestine refugees across Syria are now in urgent need of assistance.

The panel pointed to comparatively more reports of killings by anti-government armed groups during the period under review.

Most accounts emanated from Damascus, the capital and Syria's biggest city Aleppo.

Several of those interviewed also spoke about killings in Dara'a, Homs and Dayr az Zawr.

"One of those interviewed was an eyewitness to a killing at a factory with a predominantly Christian workforce.

"In early September, members of an armed group entered the factory, shouting 'We know who you are and which region you come from. We ask you to leave this factory and your region. Otherwise you will be in danger.' The director of the factory was then shot dead.

"Another eyewitness detailed the execution of pro-government Sunnis [Muslims] by the Al-Omari brigade in villages outside Dara'a city."