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BEIRUT, May 25 (Reuters) - At least 50 people, including 13 children, were killed when Syrian forces attacked the town of Houla in Homs province on Friday, the Syrian Observatory for Human Rights and activists said.

Activists said clashes erupted in the town when Syrian forces opened fire on a protest against the rule of President Bashar al-Assad and killed one protester.

"The soldiers are shelling Houla right now, the casualties are huge," said activist Ahmad Kassem. He said opposition fighters fired back, inflicting casualties on the soldiers and destroying five tanks.

Houla is a cluster of four villages and towns north of Homs.

(Reporting by Mariam Karouny; Editing by Tim Pearce)