The 193-nation UN General Assembly is planning to meet next week to discuss the escalating crisis in Syria and the recent massacre in the town of Houla, reflecting the growing international outrage over the killings, envoys said on Friday.

International mediator Kofi Annan and UN human rights chief Navi Pillay are expected to address the assembly on Thursday, UN diplomats told Reuters. Annan will also speak to the 15-nation UN Security Council that day about the lack of progress implementing his six-point peace plan.

News of the assembly meeting emerged after the UN Human Rights Council in Geneva condemned Syria on Friday for the massacre in Houla and called for a UN investigation to identify the perpetrators and gather evidence for possible criminal prosecution.

Speaking on condition of anonymity, diplomats said that the meeting would be informal but was intended to demonstrate to the Syrian government that the vast majority of UN member states find the recent mass killings believed to be caused by the government and allied militia unacceptable and repulsive.

"I can confirm that Kofi Annan and Navi Pillay will address an informal session of the General Assembly next Thursday," a diplomat said.

Nihal Saad, spokeswoman for Nassir Abdulaziz al-Nasser of Qatar, president of the General Assembly, said that discussions about such a meeting were still underway but nothing has been decided.

It was not clear if the assembly planned to adopt a resolution or declaration of some kind. While General Assembly decisions are not legally binding, it represents almost all nations on the planet and has the ability to ratchet up political pressure on Damascus.

Syria has complained repeatedly about Nasser, accusing him of using the assembly to push Qatar's agenda. Qatar is one of the harshest critics of Syrian President Bashar Assad and has suggested it could arm the rebels.

Damascus has accused Qatar and Saudi Arabia of arming the rebels, who it says are terrorists.

More than 100 men, women and children were massacred in Houla last week, most of them shot at point-blank range or slashed with knives.

UN peacekeeping chief Herve Ladsous said earlier this week that the people who died from artillery and tank fire were clearly victims of government shelling while the others most likely killed by pro-Assad "shabbiha" militia.

Damascus has blamed the massacre on the opposition, which Assad has tried unsuccessfully for 14 months to crush, killing over 10,000 people in the process, according to the United Nations. Russia, which has used its veto powers to prevent the Security Council from sanctioning Syria, blames Islamist militants for the Houla massacre.