HK shares jump on financials; Sinopec up on low oil

* Financial, energy stocks lead Hong Kong gains * Investors cautious amid slowing Chinese growth * Airlines, refiners cheer lower oil

(Updates to midday)

HONG KONG, July 17 (Reuters) - Hong Kong shares jumped 2.6 percent on Thursday, with financial and energy stocks leading the rally after a big U.S. bank posted surprisingly strong results and oil prices fell further.

Financial stocks rose after Wells Fargo (WFC.N: Quote, Profile, Research), the No. 5 U.S. bank, reported earnings that beat analyst estimates, sending shares in HSBC (0005.HK: Quote, Profile, Research) and ICBC (1398.HK: Quote, Profile, Research) 3.2 percent higher, and lifting China Construction Bank (0939.HK: Quote, Profile, Research) 4.3 percent.

Bank of China (3988.HK: Quote, Profile, Research) gained 2.1 percent, as investors shrugged off a report by CLSA that the Chinese lender may hold roughly $20 billion worth of bonds issued by troubled U.S. mortgage lenders Fannie Mae (FNM.N: Quote, Profile, Research) and Freddie Mac (FRE.N: Quote, Profile, Research).

The Hang Seng Index .HSI rose 545.08 points to close the morning session at 21,768.58, off a high of 21,892.53 hit earlier in the day. The index is still down 22 percent so far this year and is 32 percent off an all-time high hit last October.

"The morning rally was no surprise to the market, but the index failing to advance further suggested investors were still cautious and lack confidence in the U.S. market," said Alfred Chan, chief dealer at Cheer Pearl Investment.

The China Enterprises Index .HSCE of top locally listed Chinese firms rose 3.74 percent, but concern over high Chinese inflation and slowing economic growth brought stocks off early highs. [ID:nPEK199843]

Mainboard turnover increased to HK$36.8 billion ($4.7 billion) from HK$32.6 billion at midday on Wednesday.