BEIRUT, May 27 (Reuters) - Islamic State militants shot dead around 20 men in an ancient amphitheater in the Syrian city of Palmyra on Wednesday, accusing them of being government supporters, a group monitoring the conflict said.
Reuters was unable to independently confirm the report from the British-based Syrian Observatory for Human Rights.
The hardline Sunni militants took control of the central city, also known as Tadmur, from government forces last week and have killed at least 200 people and taken around 600 captive, according to the Observatory.
"They executed around 20 men in the Roman amphitheater and called people to watch," said the Observatory's Rami Abdulrahman, citing sources inside the city.
Supporters of Islamic State wrote on Twitter that a number of people had been killed by the group inside the amphitheater, which forms part of the city's 2,000-year-old ruins which are a UNESCO World Heritage site.
Islamic State's takeover of Palmyra marked the first time the group had seized a Syrian city directly from government control. The other population centers it holds were mostly taken from rival insurgent groups in Syria's four-year conflict. (Reporting by Sylvia Westall; Editing by Andrew Roche)