Malawi's vice president, arrested on treason charges, is accused of involvement in a plot to assassinate President Bingu wa Mutharika, a top government minister said Saturday.

Vice President Cassim Chilumpha was arrested late Friday at his home, the culmination of a power struggle between Mutharika and his deputy. In February, Mutharika tried to fire Chilumpha, accusing him failing in his duty by refusing to attend Cabinet meetings, and disrespect. But the courts stopped the move.

Chilumpha's party, the United Democratic Front, said the charges were a "figment of the imagination."

"This is petty politics. President Mutharika is using instruments of state to harass political opponents," said party spokesman Sam Mpasuhe.

Justice and Constitutional Affairs minister Henry Phoya told The Associated Press in an interview Saturday that over the past few months, Chilumpha instructed a prominent businessman, Yusuf Matumula, to go to an unnamed foreign country "to engage a professional assassin," who was described by Phoya as "white" but was not otherwise identified.

Matumula, also arrested on treason charges Friday, is a close ally of former president Bakili Muluzi, a former ally turned rival to the current president.

Phoya said the vice president, Matumula and the would-be assassin had "extensive discussions" at the vice-president's official residence and that Chilumpha promised the hit man millions of dollars worth of government contracts once he succeeded Mutharika.

Under Malawi law, the vice president automatically takes power once the office of the president is vacant through death, incapacitation or impeachment.

The meetings were secretly recorded, said Phoya.

"The audio on the tapes is crystal clear," he told The AP.

The minister said the would-be assassin had been to Malawi "on several occasions to plan the assassination mission," which was meant to take place in March.

"But something went wrong and the assassin grew cold feet. ... Security officers have since recorded a written statement from him where he revealed all," he said.

He said the man would be key state witness in the treason case against the vice president and Matumula.

After Chilumpha's arrest, his lawyer Fahad Assani said the treason charge was "the continuation of political vindictiveness."

He said meetings at which Chilumpha was accused of conspiring to topple the president were "normal political meetings."

There was no immediate comment from Assani on Saturday.

Mutharika, a 72-year-old former economist elected in 2004, has won widespread praise from international institutions and donor governments for pushing through economic reforms and clamping down on corruption in this impoverished southern African country. But he has alienated many former allies, including his predecessor, Muluzi, whom he accused of plotting to assassinate him.

Phoya said in addition to the president, a number of senior Cabinet ministers and government officials also were lined up for assassination. He did not name them, he said, "for fear of causing alarm."

"After the president's death there was supposed to be a number of fake armed robberies where the targeted people were supposed to be killed," he said. "The plot was quite elaborate."