MANAMA, Bahrain (AP) — Security forces in Bahrain have fired tear gas and stun grenades to break up protest marchers after calls by anti-government groups to snarl the Gulf nation’s capital with demonstrators.

Authorities set up checkpoints and expanded patrols across Manama before rallies Monday to mark an annual commemoration for two protesters killed in 1994.

Separate groups of hundreds of protesters were chanting in the narrow streets of the city’s traditional market district. Some of the crowds were dispersed with tear gas and volleys of stun grenades.

It’s the latest attempt by Shiite-led protesters to stage marches in the heart of the capital.

More than 55 people have been killed in unrest since February 2011, when Bahrain’s majority Shiite escalated their fight for a greater political voice in the Sunni-ruled kingdom.