Protesters in Malawi have padlocked the offices of the electoral commission in an effort to force its head to quit after the Constitutional Court annulled last year's presidential election.

Hundreds of demonstrators marched 5km (3.1 miles) to the commission's offices in the commercial capital, Blantyre, and locked its entrance gates with large, rusty chains.

Thousands of people did the same in the capital, Lilongwe, handing over the padlock's key to an army officer.

The court found serious irregularities in the poll, including the use of correction fluid on tally sheets.

The head of the electoral commission insists there was no wrongdoing.