Malawi’s President Peter Mutharika is leading his rivals after the counting of 75 percent of votes in Tuesday's fiercely contested election, partial results released by the electoral commission show.

The 78-year-old Mr Mutharika has so far obtained 40 percent of votes cast compared with the 35 percent of main opposition leader Lazarus Chakwera, and the 18 percent of Vice President Saulos Chilima, according to the partial results.

“It feels excellent. The results are within our predictions but certainly we are not naive enough to celebrate before the final whistle is blown,” Ben Phiri, the campaign manager of Mr Mutharika’s Democratic Progressive Party (DPP), told AFP news agency.

Mr Chakwera warned on Wednesday of attempts to rig the poll, saying counting by his Malawi Congress Party (MCP) puts him in the lead.

Malawi has a winner-takes-all system, with no run-off election.

Corruption was a major issue during the campaign, with the opposition arguing that it had worsened since Mr Mutharika became president five years ago.

Mr Mutharika himself got sucked into an alleged bribery scandal but he was cleared by the country's anti-corruption watchdog.

Nearly $4 million from a businessman embroiled in a contract controversy with the Malawi police found its way into a DPP bank account to which the president is the sole signatory.

Mr Mutharika always denied any wrongdoing and returned the money.