Burundi has blocked social media platforms on election day as voters choose a leader to replace long-serving president Pierre Nkurunziza.

Facebook, WhatsApp and Twitter are not accessible.

Only those using Virtual Private Networks (VPN), which mask a user’s identity, can access the social media sites.

Polling stations for the election opened early on Wednesday morning.

The build-up to the poll – in which seven candidates are vying to replace President Nkurunziza – has been marred by violence and accusations that the vote will not be free and fair.

The electoral commission has approved representatives from 53 foreign embassies, including some from the African Union, as poll observers.

President Nkurunziza will be stepping down after 15 years but he will transition to a newly created position, “supreme guide to patriotism”.

Of the seven candidates contesting the presidency, Evariste Ndayishimiye, candidate for the governing CNDD-FDD party, and main opposition leader Agathon Rwasa, are seen as the favourites.

Whoever wins will be required by law to consult Mr Nkurunziza on matters of national security and national unity.