SYDNEY (Reuters) - Two Chinese companies sunk by 15% in their Hong Kong initial public offerings (IPO) debuts on Tuesday, while a small Chinese petroleum refiner soared nearly 30% as sentiment towards new share sales in the city remains volatile.

Chenqi Technology opened down 14.3% and Shanghai Voicecomm sunk 15.4% in early trade on Tuesday.

Ruichang International, which raised just HK$131.1 million ($16.78 million), found support, though, with its shares trading as high as HK$1.35 each compared to HK$1.05 in the IPO.

The Hang Seng Index was up 1.3% and tech index rose 2.1% on Tuesday.

Chenqi raised HK$1.01 billion ($129 million) and Shanghai Voicecomm raised HK$664.02 million ($85.0 million), according to their respective regulatory filings.

($1 = 7.8116 Hong Kong dollars)

(Reporting by Scott Murdoch in Sydney and Donny Kwok in Hong Kong; Editing by Tom Hogue)

By Scott Murdoch and Donny Kwok