Several Chinese companies are rethinking fundraising plans in Hong Kong as anti-government protests rock the city — an ominous sign for its future as a financial gateway between Asia's largest economy and the rest of the world.

One company scrapped preliminary preparations for a $500 million initial public offering in Hong Kong partly because of the unrest, and will instead pursue a U.S. listing, according to a senior banker on the deal, who asked not to be named discussing private information. Another banker said at least two companies are considering the same move for IPOs worth a combined $1 billion, adding that final decisions will depend on market conditions and whether the turmoil in Hong Kong eases.

While the deals amount to a small portion of the money raised by Chinese businesses in Hong Kong in recent years, they bode ill for the city's status as one of the world's premier financial hubs.