A mother and her son have died in a fire after a petrol bomb was thrown at an office of the opposition UTM party in Malawi's capital, Lilongwe.

The family lived in the same building as the UTM office, which came under attack at around midnight when they were asleep.

The mother awoke and tried to save her four children from the flames, witnesses said.

Three of the children survived and are being treated for burns in hospital.

UTM is the party of Vice-President Saulos Chilima, who has fallen out with President Peter Mutharika.

He is standing as a running mate to Lazarus Chakwera, the leader of the main opposition Malawi Congress Party (MCP), in elections scheduled for July.

Political violence has been on the increase ahead of the poll, called after the Constitutional Court annulled those held last May.

The head of the European Union delegation in Malawi, along with other foreign diplomats, have issued a joint statement condemning the political violence.

“We have been shocked by the recent acts of violence apparently fuelled by political motives, and are deeply saddened,” it said.

“We support those calling for restraint and hope that all cases of violence are investigated comprehensively and transparently in line with the laws of Malawi, so that those responsible can be brought to justice,” the statement said.

Meanwhile, President Mutharika, standing as a candidate for the governing Democratic Progress Party (DPP), has presented his nomination papers, naming Atupele Muluzi, son of former President Bakili Muluzi, as his running mate.