Protesters had called for a Day of Rage to be observed on Monday, inspired by anti-government uprisings in Egypt and Tunisia.
Helicopters circled over the capital Manama, where protesters were expected to gather in the afternoon, and there was greater police presence in Shia villages.
At least 14 people were injured in clashes overnight and on Monday, news agencies reported.
The reports said police used tear gas and rubber bullets to disperse marchers in the mostly Shia village of Newidrat in the southwest region of the island kingdom - a key Western ally. The marchers were demanding the release of those detained during earlier protests.
Nabeel Rajab of the Bahrain Centre for human rights told Al Jazeera: "We are only asking for political reforms, right of political participation, respect for human rights, stopping of systematic discrimination against Shias.
"All the demands are to do with human rights and nothing to do with the ruling family and their regime."
However, he warned that if the government resorted to violence then the people might be forced to even demand for a regime change.
"We call on all Bahraini people - men, women, boys and girls - to share in our rallies in a peaceful and civilised way to guarantee a stable and promising future for ourselves and our children," activists said in a statement issued on Twitter.
Marginalised Shias
The Bahraini ruling family had offered cash payouts in the run-up to the protest to prevent Shia discontent from bubbling over as popular revolts spread in the Arab world.
Diplomats say Bahrain's demonstrations, organised on the social media websites Facebook and Twitter, will be a gauge of whether a larger base of Shias can be drawn on to the streets. The big test will be if demonstrations take hold in Manama, where demonstrations are rare.
Shias account for 70 per cent of the population but they allege discrimination at the hands of Bahrain’s Sunni rulers.
Big protests in the Gulf Arab island state could embolden other marginalised Shias in nearby Saudi Arabia, political analysts say.
