"The alleged breaches of the most fundamental rights on such a broad scale require thorough investigation and, with respect to the perpetrators, full accountability," said a report issued by the UN Human Rights Office in Geneva.
"The fact-finding mission mandated by the Human Rights Council would contribute substantially toward these ends," it said.
UN High Commissioner for human rights Navi Pillay has repeatedly called on Syrian authorities to stop attacking civilians and allow for a fact finding team to assess the humanitarian situation in the country.
"The high commissioner thus renews her call to the government of the Syrian Arab Republic to grant the access requested."
The report said that the UN has received information indicating that Syrian security forces have perpetrated acts of torture and other cruel and inhuman treatment against persons detained in connection with the demonstrations, resulting in deaths in custody in some cases.
The report said that information received indicated arbitrary detentions have been carried out by the Syrian authorities on a massive scale.
The report said that information received by the UN depicts a pattern of violent repression against groups and individuals throughout Syria, seeking to exercise their right to assemble peacefully.
"In relation to the latter, reports of the Syrian armed forces besieging entire towns such as Deraa are of particular concern," it said.
"Reports also indicate that persons attempting to flee such towns have been prevented from doing so by Syrian security forces."
Image: Protesters use their shoes to hit defaced poster of Syria's President Al-Assad during demonstration in front of Syrian embassy in Ankara
Photograph: Umit Bektas/Reuters
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