Mr Cissé was last seen at a campaign rally according to his party
Mali's opposition politician, Soumaila Cissé, has gone missing.
His Union for the Republic and Democracy (URD) party said Mr Cissé went missing while campaigning in the central Niafunke region of the country.
He and his delegation was expected on Wednesday evening in the nearby Koumaira village but he did not turn up and he has not been reachable by telephone, UDR said.
"The party is deeply worried about the situation and urges the government, the armed forces and UN mission to help trace them,” the party said.
Mr Cissé is a former minister of finance and has run for president.
The country is preparing for parliamentary elections set for 29 March.
President Ibrahim Boubacar Keita has said the elections will go ahead despite the spread of coronavirus.
Mali has declared a state of health emergency and imposed a curfew from 2100 to 0500. All land borders have been closed.