Four Bahraini policemen were wounded in a bomb attack today near the village of Jaw, south of the capital Manama, the interior ministry said. "Terrorist blast in police bus near Jua village. 4 policemen injured and they are in a stable condition. Necessary steps are being taken," the ministry said on its Twitter account. It gave no further details. On January 1, gunmen attacked the prison in Jaw, killing a policeman and allowing 10 inmates to escape. Shiites convicted over anti-government protests in Sunni-ruled Bahrain were held at Jaw. Tiny but strategic Bahrain, home to the US Fifth Fleet, has been rocked by unrest since the authorities crushed Shiite-led protests in 2011 demanding a constitutional monarchy and an elected prime minister. You may also like to watch this video: Hundreds of Shiites have been arrested and many have faced trials over their role in the demonstrations. One of those on trial is Sheikh Issa Qassem, the country's Shiite spiritual leader. He was stripped of his citizenship last year for "serving foreign interests" -a reference to Shiite Iran. Today, clashes broke out between security forces and protesters in several Shiite villages as a new hearing in Qassem's case was underway, witnesses said. Protesters chanted anti-government slogans and carried portraits of Qassem, they said.