Opposition parties in the Maldives agreed on Saturday to field a joint candidate in September's presidential elections to challenge incumbent Abdulla Yameen, whose crackdown on dissent has alarmed the international community.

Yameen declared a state of emergency in February, a move critics say was aimed at averting his impeachment. All his main rivals have meanwhile been jailed. Saturday's announcement came after ex-president Mohamed Nasheed, who is in self-imposed exile in London, said on Friday that he would not return to run in the September 23 vote.