The REPUBLIC of BURUNDI has ratified the Convention of The Hague 1961 on 10th June 2014. It will take effect from 13th February 2015 - so that after that date Notarised Documents should not require Consular legalisation, and instead the Apostille stamp of the Foreign and Commonwealth Office is required.
There are rumours that three further Countries will accede to the Convention shortly, being Vietnam, Qatar and Brasil, but I have found no definite confirmation of this as yet.