Presidential elections in the crisis-hit central African nation of Burundi have been postponed to July 21, nearly a week later than originally scheduled, the presidency announced Saturday.

A decree signed by President Pierre Nkurunziza, whose controversial bid to stand for a third consecutive five-year term has sparked weeks of civil unrest, said the polls would be moved from July 15 to July 21, with campaigning extended until the evening of July 18.

The five-nation East African Community (EAC), which has been trying to mediate an end to the crisis, on Monday called for elections to be delayed by two weeks, to July 30, to allow time for more talks between Nkurunziza's ruling CNDD-FDD party and opposition groups.

Parliamentary polls, in which the CNDD-FDD scored a landslide win, were held on May 29 but boycotted by the opposition and internationally condemned.

Opposition and rights groups say Nkurunziza's re-election bid is unconstitutional and violates a peace deal that ended a dozen years of civil war in the landlocked, impoverished nation in 2006.

They also argue that weeks of protests and a violent crackdown by security forces mean free and fair elections are impossible.

The country has also been left without most of its independent media outlets, after several radio stations were attacked and destroyed in fighting during an attempted coup against Nkurunziza in May.

Over 70 people have been killed in more than two months of protests, with over 158,000 refugees fleeing to neighbouring countries, according to the latest UN figures.