Malawi’s Supreme Court has upheld the invalidation of last year's presidential election results and ruled that Peter Mutharika was not duly elected.

In February, the Constitutional Court nullified the results after the opposition parties challenged them.

Mr Mutharika had been announced the winner of last May's election with 38.5% of the vote. Opposition party leader Lazarus Chakwera came second with 35.41%.

But the Constitutional Court judges ruled that the vote was marred by irregularities, and ordered a new election.

In Friday's ruling the Supreme Court also agreed with the Constitutional Court that none of the candidates had obtained a majority of votes.

Justice of Appeal Frank Kapanda said the court found the extent of irregularities in the May elections were "not only serious but also troubling".

The court also criticised the Attorney General as acting in a way that was not consistent with the constitution.

It further said the 150-day transition period between the lower court ruling and the election re-run in July was unnecessarily long.

Since the disputed results were announced there have been regular anti-government protests. Some of these have resulted in looting and the destruction of property, including government offices.

On Thursday, a mother and her son died after an opposition office was petrol-bombed while they were asleep in the same building.