UPDATE 11-Credit Suisse faces more upheaval after chairman's sudden exit

* Chairman Antonio Horta-Osorio apologises for personal actions

* Quits within one year after taking charge

* Bank appoints former UBS executive Axel Lehmann as chairman

* Lehmann says bank's strategy is not under discussion

* Credit Suisse announced big revamp in November (Updates share price, adds new analyst comment, background on Horta-Osorio, details on probe)

By Anshuman Daga and Oliver Hirt

SINGAPORE/ZURICH, Jan 17 (Reuters) - Credit Suisse will stick to its strategic overhaul despite the abrupt departure of its mastermind Antonio Horta-Osorio following an internal probe into his personal conduct, including breaches of COVID-19 rules, the bank's new chairman said on Monday.

Horta-Osorio leaves less than nine months after he joined the bank to help it deal with the implosion https://www.reuters.com/business/finance/spies-lies-losses-credit-suisses-scandals-2021-11-04 of investment firm Archegos and the insolvency of British supply chain finance company Greensill Capital, while it was still reeling from the 2020 exit of CEO Tidjane Thiam over a spying scandal https://www.reuters.com/article/us-credit-suisse-spying-ceo-idUSKBN2010L3.

The Portuguese banker unveiled a new strategy for Switzerland's no. 2 bank in November to focus on wealth management, rein in its investment bankers and curb a freewheeling culture.

"In the years ahead the strategy will be reviewed regularly, but at the moment it's not an issue at all," Axel Lehmann, the Credit Suisse board member picked to replace Horta-Osorio, told Reuters in an interview, his first with the media since his appointment.

The bank's shares were down around 1.6% in early afternoon trade.

Horta-Osorio's personal conduct has recently come under scrutiny, after he breached COVID-19 quarantine rules https://www.reuters.com/business/exclusive-credit-suisse-finds-second-breach-covid-19-rules-by-chairman-sources-2021-12-29 twice in 2021 - an embarrassment for the former Lloyds chief executive who has said every banker needed to be a risk manager.

"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," the Portuguese banker said in a statement issued https://bit.ly/3fC7Flb by Credit Suisse on Monday.

"I therefore believe that my resignation is in the interest of the bank and its stakeholders at this crucial time," he said.

Credit Suisse said Lehmann had taken over with immediate effect. It gave no details on an investigation commissioned by its board.