Bahraini police fired tear gas and rubber bullets at protesters marching toward the landmark Pearl Square in the country's capital, two days after authorities lifted emergency rule.
The square was the focus of weeks of Shiite-led protests against the Gulf nation's Sunni rulers earlier this year.
Witnesses in the tiny island kingdom said there were no immediate reports of casualties among the hundreds of opposition supporters who took their grievances to the streets for the first time since martial law was imposed more than two months ago.
The country's security force moved against the protesters shortly before Formula One's governing body deemed the kingdom safe enough to host the Bahrain Grand Prix in October.
The annual F1 race has been Bahrain's most profitable international event since 2004, when the nation became the first Arab country to stage the Grand Prix.
Bahrain organisers insisted they are ready to host the race this year despite the deadly crackdown. The season-opening March race was postponed because of the political unrest.
Also, thousands of mourners gathered at a cemetery in the capital, Manama, to bury a protester who died in a hospital earlier in the day of injuries from a demonstration in March.
The death of 63-year-old Salman Abu Idris raised to at least 31 the number of people killed since the campaign for greater rights and freedoms began in the Western-allied nation in February.
Bahrain is home to the US Navy's Fifth Fleet, and the US has called on its leaders to make reforms in an effort to meet at least some of the protest movement's demands.
The government lifted emergency rule on Wednesday, pulling back tanks and soldiers from the heart of the capital. But authorities warned they were not easing pressure on anti-government protesters. Opposition groups called supporters to return to the streets, the first such appeal since the military overran the protesters' encampment at Pearl Square after martial law was imposed in mid-March.