A former Zambian minister and fierce critic of President Edgar Lungu will face trial after pleading not guilty to fraud charges on Monday, following his arrest last week.

Investigators accuse ex-foreign minister Chishimba Kambwili of forging a signature on an official document and he appeared in court surrounded by hundreds of police officers who blocked access to the hearing.

“I understand the charges your honour and I plead not guilty,” lawmaker Kambwili, 50, told the court, denying the alleged offences which court documents showed date back to October 2013.

Magistrate David Simusamba set the trial date for March 6.

Kambwili has previously accused Lungu of corruption and theft and, while still a member of the president’s party, he supports the breakaway National Democratic Congress bloc.

“Lungu is drunk with his corruption and he is getting confused day by day, and those saying Lungu is not corrupt are foolish,” Kambwili said following his arrest on Tuesday.

“I want to tell you Lungu – I know you are listening – all those monies you are getting… you will not enjoy it. We know you, Lungu and your family, and we are watching you.”

Lungu has denied accusations that he is creating a dictatorship in Zambia, and has accused rivals of trying to overturn last year’s election results.

The southern African nation was last year rocked by soaring tensions that also saw a spate of arson attacks, some opposition legislators boycotting parliament and the barring of an overseas political observer.

“I am extremely excited that the matter has come to court. As you know there has been so much mud thrown at me,” said Kambwili.