Tensions in the Gulf were already escalating after Iran condemned the decision to bring in forces from neighbouring states. Tehran said the arrival of around 1,500 troops was "unacceptable".
Bahrain TV said the king "authorised the commander of the state's defence forces to take all necessary measures to protect the safety of the country and its citizens". Hours before the announcement, the capital was in lockdown with stores and schools shuttered and main roads blocked by police.