* Shanghai boosts; Japan stocks still in corrective phase
* Oil price surge buoys recovery hopes, oil stocks gain
* Truckmakers, Akebono Brake jump on brokerage upgrades
* Eyes on Japan's Aug 30 election
By Aiko Hayashi
TOKYO, Aug 20 (Reuters) - Japan's Nikkei average climbed 1.8 percent on Thursday to bounce back from a three-week closing low, with investors encouraged by a rebound in Chinese shares and gains in resource shares after crude oil surged.
Truckmakers' shares climbed after a brokerage upgrade, with Isuzu Motors adding 5.4 percent, and trading houses gained on strong metals prices.
Investors took heart after the Shanghai Composite Index jumped more than 3 percent after falling to its lowest close in two months on Wednesday. That drop had led the Nikkei to book its lowest close since late July.
Despite Thursday's bounce, however, analysts said the market is ripe for a correction after the Nikkei's gains of more than 40 percent from its March lows, with some saying investors had likely used the drop in Chinese stocks as an excuse to lock in profits.
"Sentiment is still fragile as both Japanese and U.S. stocks are in a natural corrective phase," said Mitsushige Akino, chief fund manager at Ichiyoshi Investment Management.
"Investors also lack trading factors to push the market much higher after having factored in the outlook for an economic recovery, and that's why they tend to focus on anything that can be seen as a selling signal."
In moderate trade, the benchmark Nikkei rose 179.41 points to 10,383.41, while the broader Topix gained 1.6 percent to 958.59.
Chinese shares had slid 4.3 percent on Wednesday as nervous investors pulled out on worries that a 20 percent slide in just two weeks would deepen further.
Most in the market said they felt Japan's dip this week was probably still within the range of a natural fluctuation, with support set to hold around 10,100 -- roughly where the 25-day moving average comes in.
"Investors in Chinese stocks are also taking profits partly due to concerns about a tighter policy after they had rallied sharply already," Akino said.
Along with Chinese stocks, Japan's general election on Aug. 30 is another big focus, market players said.
Opinion polls show the opposition Democratic Party well ahead of the conservative ruling Liberal Democratic Party (LDP) in the Aug. 30 race for the lower house of parliament, raising the prospect that the business-friendly LDP will lose power for only the second time in its 54-year history.
The Asahi newspaper said on Thursday that the Democrats could win about 300 of the 480 seats, though things could shift in the final days of the race.
"Until Japan's election is over, stocks may find it hard to move. The market just wants a decision fast, but if the LDP won it'd be quite a surprise and stocks would probably tumble," said Koichi Ogawa, chief fund manager at Daiwa SB Investments.
ENERGY, AUTOMAKERS JUMP
Energy shares powered higher after oil's surge on Wednesday when U.S. government data showed a steep drop in crude imports and inventories, though crude steadied on Thursday.
The surprising drop in stockpiles lifted Wall Street on views it could suggest an improving demand outlook and economy, but analysts said higher prices were a two-edged sword.
While higher oil prices reflect rising demand and a healthier economy they also raise costs and can discourage consumer spending.
Oil and gas field developer Inpex gained 2.9 percent to 721,000 yen, while distributor Nippon Oil rose 1.9 percent to 531 yen.
Trading houses rose on both the oil gains and a recovery in metals prices, with Marubeni climbing 2.8 percent to 474 yen and Itochu Corp adding 2.2 percent to 665 yen.
Isuzu and Hino Motors shot up after Nikko Citigroup upgraded them to "hold" from "sell", saying truckmakers' earnings could turn around in the second half of the business year on better overseas demand than the companies had originally foreseen. Isuzu climbed to 197 yen and Hino Motors advanced 5.1 percent to 391 yen.
Shares of auto parts maker Akebono Brake Industry soared 15.4 percent to 748 yen after Daiwa Institute of Research lifted its rating to "Neutral" from "Bearish", saying the likelihood of returning to the black in the financial year to March 2010 has increased partly due to deeper cost cuts.
Unicharm Corp, the top Asian manufacturer of diapers and sanitary goods, climbed 3.4 percent to 8,180 yen after the Nikkei business daily reported the company would enter the U.S. diaper market through a joint venture with Swedish peer Svenska Cellulosa AB.
Some 2.1 billion shares changed hands on the Tokyo exchange's first section, roughly in line with last week's daily average.
Advancing stocks outnumbered declining ones by nearly 5 to 1. (Additional reporting by Elaine Lies; Editing by Michael Watson)