* Navi Pillay calls for crime suspects to be judged
* Urges international community to take "protective action"
GENEVA, Sept 10 (Reuters) - U.N. human rights chief Navi Pillay on Monday blamed both sides in the Syrian conflict for killings and other violations and said that justice would eventually catch up with them.
She said that the international community must take "protective action" in the face of what may amount to war crimes and crimes against humanity, but stopped short of calling for a no-fly zone or military intervention.
"The use of heavy weapons by the government and the shelling of populated areas have resulted in high numbers of civilian casualties, mass displacement of civilians inside and outside the country and a devastating humanitarian crisis," Pillay said in a speech to the U.N. Human Rights Council in Geneva.
She was equally concerned at violations by anti-government forces, including murder, extrajudicial execution and torture, and their increased use of improvised explosive devices.
Pillay, a former U.N. war crimes judge, repeatedly has called for Syria to be referred to the International Criminal Court, but such a referral can only be effected by the U.N. Security Council, which is split on how to deal with Syria.
China and Russia oppose any attempt to lay the blame for the crisis on President Bashar al-Assad.
"A referral will make it abundantly clear to all actors in Syria that they will not escape justice and will be held accountable for alleged violations of international human rights law and international humanitarian law," Pillay said on Monday in a separate speech she made to a discussion on Syria.
"Opposition forces should be under no illusion that they will be immune from prosecution," she added.
Amateur video posted on YouTube on Monday showed images of 20 dead Syrian soldiers, blindfolded and handcuffed, after they were apparently executed in the northern city of Aleppo. It was not possible to verify the videos' authenticity.
Muhanad al-Hassani, a Syrian lawyer and activist who fled the country a year ago after serving two years in prison, said that the Assad government was driving people to violence and that major powers shared the blame for failing to intervene.
"Our revolution is not a religious revolution. It is a revolution of an oppressed people. For 50 years the West has supported this dictatorship," he told the Geneva discussion.
"People are being led towards radicalisation. We do not want that in Syria. I was for peaceful revolution until the last moment," al-Hassani said. "The protection of civilians is a legal and moral responsibility, a priority."
So far 64 journalists have been killed in the conflict, said Syrian journalist Amer Matar, who spent six months in jail before fleeing his homeland earlier this year via Jordan.
"People were tortured daily. All my colleagues, journalists were in prison because they were covering events truthfully."
EVIDENCE AND TESTIMONY
The Human Rights Council has repeatedly condemned Syria's government for its handling of what began as a peaceful protest against the government and has escalated into civil war. China, Russia and Cuba have consistently voted against its resolutions.
Independent U.N. investigators, in a report last month , said that Syrian government forces and allied militia have committed war crimes including murder and torture of civilians in what appears to be state-directed policy.
The United States called on Monday for the mandate of the inquiry, which expires later this month, to be extended so that it continues to collect evidence and testimony.
"The onus is upon this Council to ensure that those who commit such heinous human rights violations are investigated and identified so that perpetrators can be held accountable," U.S. ambassador Eileen Chamberlain Donahoe told the Council.
Lotte Leicht of the group Human Rights Watch said that the independent investigators must be allowed to continue their work despite what she called "stonewalling" in the Security Council.
"It is key that the commission of inquiry gather, analyse and preserve evidence it collects for the purpose of it being made available for possible future prosecutions," Leicht said.
The Syrian Observatory for Human Rights, an opposition watchdog based in London, says more than 27,300 people have died in an uprising that has lasted more than 17 months.