Mozambique’s Interior Minister Pascoal Ronda said on Tuesday night that at least 21 people had been killed in riots that erupted after the Supreme Court on Monday validated the election victory of the long-ruling Frelimo party, Reuters reports.

The decision by Mozambique’s Constitutional Council has prompted opposition groups and their supporters to organise fresh protests across the country over what they say is electoral fraud.

The minister added in a statement to public broadcaster TVM that 78 people have been arrested so far, while authorities have stepped up security across the country. The army and defence forces will increase their presence at vital and key points, he added.