U.N. Secretary General Ban Ki-moon says the "stepped-up security crackdown" by the Syrian government is leading to "massive violations of human rights" by both sides of the conflict.
In a report to the U.N. Security Council Friday, Ban said the presence of unarmed U.N. observers is "having a calming effect" but the overall level of violence in Syria remains "quite high".
Earlier Friday, the activist group the Syrian Observatory for Human Rights said government forces had killed more than 50 people, including 13 children, in Houla in Homs province.
The group said government forces also shot and killed four people in the flashpoint Hama region and another person in southern Daraa province. Details of the incidents were not available.
The killings came as Friday prayers ended in Syria, and protesters spilled on to streets in major cities including Damascus and Aleppo, calling for the resignation of President Bashar al-Assad.
Although hundreds of United Nations observers are in the country, there appears to be little sign that violence between rebels and government forces is subsiding.
The continued unrest has strained a six-week-old cease-fire which is part of a peace plan brokered by international envoy Kofi Annan.
The Reuters news agency quoted an Annan spokesman as saying the envoy would travel to Syria "soon" for what would be his first visit since presenting the peace plan in March.
And the violence is having an impact in northern Lebanon, where ethnic clashes between opponents and supporters of Assad have left at least 11 dead and over 100 wounded in recent days .
VOA's Scott Bobb reports from northern Lebanon that tensions there are still running high.
"Historically, Syria has wielded a great deal of influence in Lebanon, its smaller neighbor, and even occupied it for years up until a few years ago. Although Syria did withdraw a few years ago, the influence is still there and it is resented by many people. In this particular case, in Tripoli, what happened was a Salafist sheikh, the Sunni Islamist, was killed at a checkpoint. He was known to be opposed to the regime of Bashar al-Assad in Syria, and this raised tensions with the local Allawite community, to which President Mr. Bashar al-Assad belongs."
A dozen Lebanese Shi'ite pilgrims who were kidnapped in Syria this week while returning to Lebanon from Iran were released on Friday. While it was unclear who was behind the incident, it set off protests in Shi'ite areas of Beirut and a regional diplomatic spat.
"This is again another irritation or aggravation of the sectarian fault lines that exist in both societies. These are Shi'ite pilgrims in Syria who were captured by someone. It was claimed it was by the Syrian rebels, although the rebels denied it. Some of the anti-Damascus people [in Lebanon] said this was just one more act by the Syrian regime to try to sow dissent and curry favor for its cause," Bobb said.