BEIRUT -- An activist group says Syrian security forces have killed four people in the restive central city of Homs.

The London-based Syrian Observatory for Human Rights says security forces also detained dozens of people in Homs, which has been the scene of mass protests since an uprising against President Bashar Assad's regime began in mid-March.

Syria's state-run news agency SANA said Tuesday that authorities detained 144 wanted people and confiscated large amounts of ammunition and assault rifles in Homs.

The uprising against Assad began amid a wave of anti-government protests in the Arab world that toppled autocrats in Tunisia, Egypt and Libya.

Assad has reacted with deadly force that the U.N. estimates has left nearly 3,000 people dead.