About 10 Syrian opposition groups announced Monday they were suspending talks about planned peace negotiations this month in the Kazakh capital Astana, due to "violations" by Damascus of a four-day old truce.

"As these violations are continuing, the factions announce... the freezing of all discussion linked to the Astana negotiations," they said in a joint statement, referring to talks planned for late January organised by Russia, which supports the Syrian regime, and Turkey which backs the opposition.

The Syrian regime and its allies have violated a ceasefire 77 times since it went into effect late last week, the Syrian Network for Human Rights (SNHR), a London-based NGO, declared in a report issued Monday.

"The Syrian regime committed 72 [ceasefire] violations while Russia was responsible for five breaches committed when it shelled central Hama and northern Aleppo," the report asserts.

According to the SNHR, its report is based on personal interviews with survivors of recent attacks, the relatives of victims and eyewitnesses.

"Among the 77 violations cited, 68 were in the form of fighting operations and nine were in the form of detentions," the report reads, noting that most regime violations had occurred in Syria's Homs province.

The NGO also called on Russia -- as a guarantor of the ceasefire agreement -- to pressure its allies in Damascus and Tehran to abide by the terms of the deal.

Last Friday night, the ceasefire took effect across Syria, which since 2011 has been locked in a devastating civil war.