Vietcombank, Vietnam's top lender by market value, plans to issue new shares to foreign investors, equivalent to 10 percent of existing stock and worth an estimated $510 million, aiming to meet capital requirements.

The lender is working with Credit Suisse to study potential investors and expects a deal to come this year, bank board member Le Thi Hoa told Reuters.

Japan's Mizuho Bank, which owns 15 percent of Vietcombank, will buy more shares to at least maintain its current ownership ratio, and may increase its ownership to as much as 20 percent, she said.

Vietcombank will look for another foreign investor, Hoa said, as Mizuho cannot buy all of the shares to be issued due to Vietnam law that prevents one foreign investor from holding more than 20 percent of a bank. Total foreign ownership is capped at 30 percent.

A spokesman for Mizuho was not immediately available for comment due to a public holiday in Japan.

"We are in contact with investors that Credit Suisse introduced," Hoa said, adding that a formal approach is pending approval of the plan at its April 15 general shareholders meeting.

The lender had $30.2 billion in assets as of end 2015. The new share issue is worth $510 million at current market prices.

Dau Thi Van Anh, banking analyst at Ho Chi Minh Securities, said that while details on pricing and trading limit conditions for the new shares are not yet available, the issue would be worth considering given the quality and credibility of the lender.

"VCB has always been the top choice among Vietnamese listed banks, given its leading position based on competitive advantages like low capital costs, diverse sources of revenue, careful risk management and healthy assets," Van Anh said.