The brutal crackdown, which followed an army pledge to restore order through "strict measures" after a deadly police raid, led the United States and Britain to ask nationals to avoid all but essential travel to the Gulf kingdom.

Crown Prince Salman bin Hamad al-Khalifa promised to open a national dialogue once calm return, and soon afterwards King Hamad formally announced that he had assigned his heir to start those discussions.

US President Barack Obama condemned the violence in a phone conversation with the king, a key regional ally of Washington.

Obama said "the stability of Bahrain depends upon respect for the universal rights of the people of Bahrain, and a process of meaningful reform that is responsive to the aspirations of all Bahrainis," according to a White House statement.