Malaysian banking circles are in shock after the sudden resignation of a key Maybank executive - a move that could trigger a major corporate shake-up at the country's biggest bank.

The Straits Times understands that Tengku Zafrul Tengku Aziz, chief executive of Maybank Investment Bank and group chief executive of Maybank Kim Eng, submitted his resignation letter to the Maybank chairman yesterday.

Mr Zafrul, who was acting head of Maybank's global banking business, is believed to be poised to join CIMB Group as deputy chief executive on Jan 1.

The chief executive of CIMB, Malaysia's second-largest bank by assets, is Mr Nazir Razak, brother of Malaysian Prime Minister Najib Razak.

Although no reason was cited in his resignation letter, it is believed that Mr Zafrul was disenchanted with Maybank chairman Megat Zaharuddin Mohd Nor, who was taking a while to confirm him as Maybank's head of global banking.

Banking sources say Mr Zafrul, 40, may be in line to take over from Mr Nazir in three years.

Mr Zafrul's resignation will shock the financial sector. He was instrumental in landing big investment deals and beefing up Maybank's weak links in corporate advisory and corporate finance.

He also gave market leader CIMB Group and master deal- maker Mr Nazir some stiff competition in Malaysia's investment banking industry.

His notable big-ticket deals include some of the largest listings in Malaysia and Asia last year - palm oil giant Felda Global Ventures and IHH Healthcare - and the big oil and gas merger between Sapura and Kencana Petroleum.

Mr Zafrul also played an instrumental role in the merger between Maybank and Singapore brokerage Kim Eng.

His new role at CIMB will include the job of chief executive of investment banking, a post left vacant when seasoned banker Charon Wardini Mokhzani quit to join Khazanah Nasional yesterday.

Mr Zafrul's move comes after the surprise key departure earlier this month of Mr Khairussaleh Ramli, head of Maybank's Indonesian unit PT Bank Internasional Tbk.

The resignations come after Maybank's board picked Mr Abdul Farid Alias as president and chief executive last month.

Both Mr Zafrul and Mr Khairussaleh were seen as front runners for the top posts, which were left vacant when Mr Abdul Wahid Omar stepped down to serve in Datuk Seri Najib's Cabinet as a Minister in the Prime Minister's Department, heading the Economic Planning Unit.

Mr Khairussaleh is expected to join RHB Bank as deputy chief executive officer, according to some news reports.

Banking sources suggest a few more resignations, particularly from the investment banking and stockbroking operations in Malaysia, Thailand, the Philippines and Indonesia, may follow.

Mr John Chong, Maybank Investment Bank's deputy chief executive officer and head of investment banking and advisory, is expected to to cover Mr Zafrul's duties until a replacement is found.