Hang Seng Bank shareholders were divided over HSBC's buyout proposal as investors gathered on Thursday to vote on the offer, which the British bank's chairman said would unlock more synergy.

HSBC, which owns about 63 percent of Hang Seng, offered to spend HK$106 billion buying the shares it did not already hold at HK$155 each under the privatisation plan.

If the proposal is approved, Hang Seng's shares will be delisted from the Hong Kong stock exchange from January 27.

A shareholder, surnamed Ho, bought the stocks between HK$160 and HK$170. But he said he had "no other options" but to vote to accept the offer, although it would mean suffering losses.

"It's disappointing to see [Hang Seng] suddenly being privatised when I had high expectations for the bank. I was hoping to hold the shares until the day I die," he said.

Another shareholder, surnamed Cheng, said the offer was a good deal and she would put the money gained into HSBC.

"I bought Hang Seng at HK$100 and now I'm offered [around] HK$150 per share," she said.

Peter Wong, chairman of HSBC, wrote in a newspaper that the plan was not about erasing distinctions between the two banks, but to reinforce their complementary strengths to unlock greater synergies.

He also said the move would help further bolster Hong Kong's competitiveness as an international financial centre.