Bahrain tightened security Thursday, as the three-day Formula One Grand Prix was about to get under way, with the country's Shiite opposition planning protests to seize world attention for pro-reform demands.
Demonstrations have been held during the event every year since 2011 by opponents of the ruling Sunni Al-Khalifa dynasty in an attempt to highlight those demands.
Clashes frequently erupt on the outskirts of Manama between security forces and protesters from the Shiite majority demanding that the Khalifas surrender their grip on all key cabinet posts in favour of an elected government.
This year's Grand Prix begins Friday and runs through Sunday.
On Thursday, police deployed along a main road linking Manama to the Sakhir F1 circuit in the south, as more checkpoints were set up on roads leading to Shiite villages, witnesses said.
The influential Shiite opposition bloc Al-Wefaq has called for a rally Friday on the main Budaya highway, four kilometres (2.5 miles) west of Manama, which links several Shiite villages.
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Leader Sheikh Ali Salman has urged supporters to protest "peacefully... and exploit the presence of (foreign) media attending the F1... so the world could hear the voice of the opposition and its demands and the oppression we suffer from in our country."
Al-Wefaq's peaceful rallies are usually tolerated by the authorities and rarely end in violence.
But protests by supporters of the radical February 14 Revolution Youth Coalition cyber-group often degenerate into clashes with police.
The group, accused by authorities of links to Shiite-majority Iran, called for demonstrations Friday in the Al-Seef Junction area, west of Manama, under the slogan: "Stop the blood formula."
Public security chief General Tariq Hasan said Tuesday the authorities have taken "all measures and plans" to secure the Formula One event.
Meanwhile, Amnesty International has raised concerns of a crackdown ahead of the Grand Prix.
Bahrain, home to the US Navy's Fifth Fleet, remains deeply divided three years after the Shiite-led uprising was quashed, with persistent protests sparking clashes with police, scores of Shiites jailed on "terror" charges and reconciliation talks deadlocked.
The International Federation for Human Rights says at least 89 people have been killed in Bahrain since the uprising began in February 2011.