BEIRUT, Dec 31 (Reuters) - The death toll in Syria's civil war has risen to at least 130,433, more than a third of them civilians on both sides of the conflict, but the real figure is probably much higher, the Syrian Observatory for Human Rights said on Tuesday.
The conflict in Syria began in March 2011 as peaceful protests against four decades of rule by President Bashar al-Assad's family, but turned into an armed insurgency whose sectarian dimensions have reverberated across the Middle East.
The anti-Assad Observatory, based in Britain but with a network of sources across Syria, put the number of women and children killed in the conflict so far at 11,709.
It said the death toll among rebels fighting the Assad government was at least 29,083.
Deaths among the Syrian armed forces and fighters supporting Assad were at least 52,290, including 262 fighters from the Lebanese Shi'ite group Hezbollah and 286 from other non-Syrian Shi'ite groups.
Both Sunni and Shi'ite militants from the region have joined the fight on opposite sides.
Many Sunni Muslim nations support the rebels, who are led by Syria's Sunni majority. Shi'ite Muslim states back Assad, who is from the minority Alawite sect, an offshoot of Shi'ism.
The Observatory said at least 17,000 people are being held in government prisons while more than 6,000 government supporters are in the custody of Islamist rebels.
It said the actual number of people killed and imprisoned is likely to be at least 50,000 higher, but said it could not verify those cases because the identities of the victims were hidden or missing.
The United Nations does not give regular casualty counts for Syria and has said for months that more than 100,000 have been killed. (Reporting by Stephen Kalin; Editing by Louise Ireland)