A car bomb exploded outside a Sunni mosque in a Bahrain neighbourhood where the royal court is situated but caused no casualties, Bahrain's interior ministry said.
The bomb, made from a gas cylinder, exploded late Wednesday in the parking area of the Isa Bin Salman Mosque in the Rifaa neighbourhood, south of the capital Manama, the ministry said.
"The terrorist act took place while prayers were held in the mosque," it said.
Witnesses said the blast site was close to the royal court of the Sunni dynasty that rules Shia-majority Bahrain.
Militants from the disgruntled Shia majority are usually blamed for unrest in the Gulf kingdom, where confrontations between police and Shia protesters are frequent.
King Hamad issued a statement late Wednesday condemning the attack and ordering security forces to hunt the culprits and the "instigators."
"The people of Bahrain have had enough and have run out of patience over such acts that are strange to the people of Bahrain and their morals," he said.
The latest bombing comes amid an escalation in attacks on police in Shia villages using homemade explosive devices and petrol bombs, according to authorities.
Last week, four policemen were wounded in a bombing outside the Shia village of Janabiyah, just weeks after an explosion killed a policeman and wounded two others in the area of Sitra.
Protests remain frequent in Shia villages despite a heavy-handed crackdown in March 2011 that quelled a month-long protest inspired by the Arab Spring uprisings.
At least 80 people have been killed in Bahrain since protests erupted, according to the International Federation for Human Rights.