* HK shares rise 1.3 pct to 5-mth high as Asian markets rally
* Shanghai Composite Index edges lower, holds support level
* Consumer-related plays outperform ahead of China holidays
* BYD jumps 10.7 percent, power companies extend gains (Updates to close)
By Vikram S.Subhedar and Farah Master
HONG KONG/SHANGHAI, Se..pt 17 (Reuters) - Hong Kong shares rose in healthy volume, lifting the benchmark index to a five-month high with investors riding a rally in risk assets across Asia.
The Hang Seng Index rose 1.29 percent to 21,970.86, higher on the year for the first time since mid-April. The China Enterprises Index gained 1.41 percent to 12,171.19.
A sharp rally at the start of the week following better-than-expected data from China and the U.S. helped the benchmark record its sharpest weekly gain since late February, up 3.4 percent.
With the Aussie and the euro rallying today, people were watching whether the Shanghai Composite was going to hold up, said Christian Keilland, head of trading at brokerage BTIG in Hong Kong.
"Once Shanghai bounced off the 2,595 support, momentum traders rushed in, chasing high beta stocks," said Keilland.
Beta is a measure of volatility of a particular security relative to the broader index.
Consumer-related plays rose ahead of the Mid-Autumn Festival holiday in China. Belle International Holdings Ltd, which also has a relatively high beta of 1.45, rose 4.7 percent and was the top gainer on the Hang Seng Index.
Brewers rallied with Tsingtao Brewery Co Ltd up 4.7 percent on healthy volume. Kingway Brewery Holdings Ltd jumped 10.1 percent.
Chinese car and battery maker BYD Co Ltd, which is backed by billionaire investor Warren Buffet, soared 10.7 percent amid a broad rally in auto stocks.
Large cap mainland banking shares, which have been under pressure all week on talk of more stringent capital requirements, regained ground after China's banking regulator denied having any plans to raise capital ratios.
China Construction Bank Corp rose 2.4 percent. Industrial and Commercial Bank of China Ltd was up 0.9 percent.
The week's rally on the Hang Seng Index has taken its relative strength index to 70, which indicates stocks are technically overbought and could be poised for a pullback.
SHANGHAI FIRMS
China's key stock index declined for a third straight session on lower volume as investors continued to trim positions ahead of long holidays in coming weeks.
The Shanghai Composite Index closed at 2,598.7, finding support around the 2,595 level. Analysts said the index had room to drop further but they saw near-term support around the index's 60-day moving average at 2,580.
"Recently, A shares have suffered from a lot of negative news, such as worries over a possible rise in deposit rates. This is impacting sentiment for listed companies," said Chen Xingyu, analyst at Phillip Securities in Shanghai.
Turnover was subdued as investors chose to stay away after trimming positions in previous sessions ahead of holidays.
China will see two major national holidays in the next three weeks, during which the market will be open for a combined seven trading days, with two weeks having either one or two days.
"The upcoming holidays are making investors cautious. During this time if global markets change, what do you do?," said Zhang Gang, analyst at Central Securities in Shanghai. "After the holidays we have September and third-quarter economic data, so this is not giving investors a reason to build up new positions."
Power stocks supported the index after state media reported that several Chinese provinces were considering raising electricity prices, which could be followed by others. Huaneng Power International Inc advanced 5 percent.
Financials were the biggest drag on the index with heavyweight Agricultural Bank of China Ltd down 1.1 percent falling further below its listing price. (Editing by Chris Lewis)