Belgium said Monday it has suspended aid for elections in Burundi following violent clashes between security forces and protesters against President Pierre Nkurunziza's bid for a third term.

Belgium, the biggest bilateral backer of Burundi's voting process, has also halted support for a police mission in the country, international development minister Alexander De Croo said in a statement.

"De Croo believes that in the current circumstances the payment of the remaining tranche of two million euros ($2.2 million) must be suspended," with two million euros of an overall budget of four million having already been paid out, the statement said.

It cited the fact that the EU's electoral mission in Burundi had said last week that "conditions for free elections have not been met at the moment".

Also Belgium's involvement in a police cooperation mission with Burundi, which also involves the Netherlands, "must be temporarily suspended", with the suspension of three million euros in aid out of a budget of five million.

At least 19 people have died in Burundi since Nkurunziza announced his intention to run for a third term in elections due next month, sparking weeks of angry demonstrations.