GENEVA — Credit Suisse says its chairman has resigned following an internal investigation that reportedly turned up that he had violated quarantine rules intended to fight the COVID-19 pandemic.

The resignation of Antonio Horta-Osorio, a British-Portuguese national who took the job barely eight months ago, was announced shortly after midnight today. It is the latest upheaval at the top-drawer Swiss bank that has faced an array of recent troubles, including bad bets on hedge funds and an internal spying scandal.

“I regret that a number of my personal actions have led to difficulties for the bank and compromised my ability to represent the bank internally and externally,” Horta-Osorio, 57, said in a statement from the bank, without elaborating.

“I therefore believe that my resignation is in the interest of the bank and its stakeholders at this crucial time.”

Axel Lehmann, a Swiss national and former executive at rival bank UBS who joined the Credit Suisse board in October, will take over as chairman.

Credit Suisse said Lehmann “succeeds Antonio Horta-Osório, who resigned following an investigation commissioned by the board.” It did not elaborate, and bank spokesman Dominik von Arx declined to comment beyond the news release.

Swiss media reported Monday that Horta-Osorio, a former CEO of Lloyds Banking Group in Britain, had violated quarantine rules, including traveling to Britain in December and to the Wimbledon tennis tournament over the summer.

Online news service finews.com, citing two sources familiar with the situation, reported in late December that Horta-Osorio was being investigated over allegations of breaking quarantine.