Bahraini police fired tear gas to disperse hundreds of Shiite protesters who took to the streets today on the fourth anniversary of an uprising that deeply divided the key US ally.
Police deployed heavily as men and women carrying Bahrain's red and white flag alongside portraits of detained activists chanted "Down Hamad", in reference to the Sunni king, witnesses said.
They fired tear gas and sound bombs and beefed up security around several villages and along major roads across the country, the witnesses said, without reporting any casualties.
The security measures were aimed at preventing the demonstrators from advancing towards the centre of the capital Manama, where the 2011 uprising was focussed.
Protesters burned tyres and used rocks, garbage containers and branches to block roads in the villages.
The radical February 14 Coalition, a cyber youth group, had urged demonstrations and strikes across the kingdom under the slogan "Strike of Defiance".
But the public security chief, Major-General Tariq al-Hassan, had issued a stern warning ahead of the protests.
"Action will be taken against those who spread terror among citizens or residents, put the safety of others at risk or try to disrupt the nation's security and stability," Hassan said.
Bahrain's Saudi-backed Sunni Muslim authorities crushed protests led by its majority Shiites shortly after they erupted on February 14, 2011, taking their cue from Arab Spring uprisings in the Middle East and North Africa.
Home to the US Fifth Fleet, Bahrain sits across the Gulf from Shiite-dominated Iran.
It is also one of several Arab states that backs US-led air strikes against the Islamic State group in Iraq and Syria, making it a vital Western ally.
Tensions are running high in the kingdom where a sectarian divide is deepening and there is a growing gap between the Sunni minority government and its mainly Shiite opponents.
The opposition is demanding a "real" constitutional monarchy with an elected prime minister who is independent of the ruling royal family, but the Al-Khalifa dynasty has refused to yield.
Shiite opposition leader Sheikh Ali Salman is behind bars for allegedly trying to overthrow the regime.
His arrest on December 28, shortly after he was re-elected head of Bahrain's main opposition party Al-Wefaq, has sparked near-daily protests in Shiite villages.
Attacks targeting security forces have also increased.
