HONG KONG (Reuters) - Alibaba.com Ltd shares rose more than 40 percent to a seven-month high on Wednesday after they resumed trading following an announcement that its parent Alibaba Group will take it private for about $2.5 billion at its IPO price.

Alibaba.com opened at HK$13.18, compared with its IPO price of HK$13.50 and sharply higher than its last closing price of HK$9.25 on February 8.

The opening share price is the highest intraday level since mid-July last year.

Jack Ma's Chinese e-commerce firm Alibaba Group said on Tuesday that it planned to take the Hong Kong-listed unit private, stressing the move was unrelated to any possible deal to buy back shares owned by Yahoo Inc.

Alibaba Group is offering investors HK$13.50 in cash per share, the same price as at the company's IPO in 2007.

(Reporting by Lee Chyen Yee; Editing by Chris Lewis)