The blast took place early morning in the minibus, when hundreds of Shiite Muslims were taking part in a religious procession in the area, officials told Xinhua.
The blast came a day after reports in the British media that former assistant commissioner at London's Metropolitan Police John Yates was appointed by Bahrain to help its interior ministry's security forces.
In March 2010, unidentified men hurled Molotov cocktails at the embassy compound.