At ACB's headquarters in Ho Chi Minh City, staff handed out leaflets to customers highlighting a central bank assurance that deposits in the bank were secure.

Queues at branches of other banks in Ho Chi Minh City were normal on Friday.

At ACB, a screen on the wall repeatedly showed state television footage talking about the safety of the bank, as three security trucks drew up outside with bags of cash that needed around 40 staff to bring inside.

ACB, one of the biggest banks in Vietnam, has faced a run on deposits since the government on Tuesday announced the arrest of co-founder Kien, who is accused of running illegal businesses.

Late on Thursday, ACB, which is 15 percent owned by Standard Chartered PLC , said that Chief Executive Hai, 47, had resigned.

'INTENTIONAL WRONGDOINGS'

The official Vietnam News Agency reported he had been arrested that day, accused of "intentional wrongdoings that violated state regulations on economic management, causing serious consequences."

That wording is often used in cases where a person goes on trial on corruption charges. If found guilty, a convicted person could face up to 20 years in jail.

The state news report gave no detail on the charges against Hai, who has doctorates in physics and mathematics and joined the bank in 1996. It cited police investigators as saying he would remain in detention for four months.

Some of the customers at ACB's headquarters seemed reassured by the central bank guarantee.

"I feel more confident after the support pledged by the State Bank and also because ACB is a major bank," said Pham Hoang Anh Tuan, although he was still debating whether to withdraw his gold deposits.

The price of gold rose on the domestic market earlier in the week as small savers, fearing a bank crash, saw it as a safe haven. It was lower on Friday after the central bank stopped banks from taking fresh gold deposits or lending gold to clients from Thursday.

WELL-KNOWN FIGURE

Kien, 48, is still an ACB shareholder, although he no longer has a role in its management.