Bahraini police fired rubber bullets and tear gas on Wednesday to disperse protesters who were attempting to hold a banned demonstration in Manama, the key Shiite opposition group Al-Wefaq reported.
There were no immediate reports of injuries or arrests.
Security forces prevented the small groups of people, who were chanting anti-regime slogans and demanding democracy, from reaching the Ras Rumman diplomatic quarter in the capital's business district, the source said.
The authorities said on Tuesday that they were prohibiting the demonstration, called by the Shiite-led opposition, for security reasons.
Al-Wefaq's website also called for another demonstration to be held in a suburb of the capital on Thursday, the same day an air show is to begin in the tiny Gulf kingdom.
Signup to our newsletter and follow us on Facebook and Twitter!
The incident comes just days after King Hamad introduced constitutional reforms that give more power to the elected parliament, but fall far short of the demands set down by the opposition.
A brutal crackdown on protests in mid-March led to the death of 35 people, including five security personnel and five detainees tortured to death, according to a commission appointed by the king.
Hundreds were injured.
Tensions have remained high in Bahrain since the spring, and sporadic violence has been on the upturn in recent weeks.
On December 31, a Shiite youth was hit and killed by a tear gas shell.
Bahrain's Shiite community, although a majority in the Sunni-ruled kingdom, has complained of marginalisation.