BEIRUT (Reuters) - Men in black shirts attacked protesters in central Beirut on Tuesday, destroying their camp in the square as some people ran shouting for help from security forces, according to a Reuters witness.

The men were believed to be supporters of the Lebanese groups Hezbollah and Amal.

Earlier, supporters of the two Shi'ite movements fought with protesters at a roadblock and in another part of central Beirut, leading police to step in, Reuters witnesses said.

(Reporting by Ellen Francis; Editing by Samia Nakhoul)