Bahrain's crown prince said he would not attend Britain's royal wedding on April 29 because of continuing unrest in his Gulf Arab kingdom, defusing a potentially embarrassing row over his invitation.

Human rights campaigners criticising Bahrain's fierce security crackdown on anti-government protesters called on Britain's royal family to withdraw the wedding invite sent to Sheikh Salman bin Hamad al-Khalifa.

The crown prince said he had decided with deep regret to decline the invitation to the marriage of Prince William and Kate Middleton, in a letter sent to William's father Prince Charles, heir to the British throne.

Nabeel Rajab, head of the Bahrain Center for Human Rights, had criticised the crown prince's invitation, which was confirmed on Saturday.

"Is this a reward to our ruling family for the crimes they committed? We were waiting for a tough reaction from the UK, and we see this when people's blood has not even dried," Rajab said.

British human rights campaigner Peter Tatchell had said the invite was a "massive misjudgement" by Britain's royal family.

Last month, Bahrain crushed protests by declaring martial law, inviting in troops from Sunni neighbours such as Saudi Arabia and arresting hundreds of people, many of them activists or doctors.

Hundreds have been sacked from government jobs, rights and opposition groups say. Bahrain says it has targeted only those who committed crimes during the unrest in March.

Reuters