Business-to-business site operator Alibaba.com is to spin off and list one of its units in the United States.

Alibaba told the Hong Kong stock exchange yesterday that it was planning an initial public offering of HiChina Group, an Internet infrastructure service provider.

HiChina's proposed listing is currently under review by the US Securities and Exchange Commission, Alibaba said, adding that the size and price of the listing has not been finalized.

Alibaba bought an 85 percent stake in HiChina in 2009 for US$79 million in order to gain a wider customer base and enhance its ability to provide additional Internet infra-structure services to small and medium-sized businesses with e-commerce operations.

Meanwhile, Alibaba said it repurchased 3.2 million of its own shares for HK$21.5 million (US$2.76 million) yesterday on the open market.

It has already spent HK$1 billion on repurchasing shares since Alibaba's board approved a repurchasing plan in 2008. It still has HK$1 billion to continue buying shares.

The company had 68.9 million registered users and 9.2 million storefronts at the end of the first half this year.

Its shares were down 8.2 percent yesterday to close at HK$6.42.

In other news, Singapore's Temasek Holdings, Russian Internet investment firm DST Global and venture capital firm Silver Lake Partners said last week that they have agreed to buy a total of US$1.6 billion worth of shares in Alibaba's parent company, Alibaba Group, from employees, option holders and other shareholders.