BLANTYRE, MALAWI - Malawi's anti-graft body said Monday it probed alleged attempts to bribe judges tackling  a case linked to a controversial election which handed President Peter Mutharika a second term.

The opposition Malawi Congress Party (MCP) and the United Transformation Movement (UTM) have said the May 21 poll last year was marred by fraud.

Mutharika narrowly won, beating MCP candidate Lazarus Chakwera by 159,000 votes.

Opposition leaders say the result sheets were tampered with and petitioned the country's top court in August to annul the results.

Presidential election results have never been challenged in court since Malawi's independence from Britain in 1964.

Malawi's Anti-Corruption Bureau (ACB) on Monday said it had received a complaint from Chief Justice Andrew Nyirenda alleging bribes had been offered to the five judges presiding over the case.

"I can confirm that we received the complaint from the chief justice," ACB head Reyneck Matemba told AFP, adding that he could not release "names of the suspects" for the time being.

Judiciary spokeswoman Agnes Patemba confirmed the case would be handled by the ACB.  

Mutharika has dismissed doubts on the official results, which show he won 38.57 percent of the vote to Chakwera's 35.41 percent.   

UTM candidate Saulos Chilima came third with 20.24 percent.  

Sporadic demonstrations have since broken out across the southern African country, with protesters demanding the ouster of the electoral commission's head over her handling of the vote.

"There is a clear intention by some of the parties to the case to compromise the judiciary," said Malawian law professor Danwood Chirwa.

A ruling is expected by the end of January.