By Chao Deng 

China stocks fell modestly while markets elsewhere in Asia rose after the Federal Reserve stuck to a near-zero benchmark interest rate, as expected.

The Shanghai Composite opened 0.4% lower at 3773.79. The smaller Shenzhen Composite fell 0.5% to 2188.00 while the small-cap ChiNext board is down 0.8%.

On Wednesday, the Shanghai Composite snapped a three day losing streak after authorities came out earlier in the week to say they would continue to support the market and investigate recent sharp declines.

Hong Kong's Hang Seng Index is up 0.7% while a gauge of Chinese companies listed in the city gained 0.6%.

The Federal Reserve offered few clues on plans to raise interest rates for the first time in nearly a decade. Its easy-money policy, mirrored by central banks around the world, has helped fuel a rally since the global financial crisis, and a delay in raising rates could give stocks more steam.

The Nikkei Stock Average was up 1.1%, S&P ASX 200 was up 0.6% and South Korea's Kospi was off 0.2%.

In China, the second wave of selling this month, bulk of which came in an 8.5% decline Monday, appears to have helped flush out more leveraged bets in the market.

Vincent Chan, analyst at Credit Suisse, said that financing for buying stocks by informal lending channels, as tracked by one major trading system, likely dropped sharply since mid-July. Authorities have been clamping down on margin financing--the borrowing of money by brokerages and unofficial lenders to investors--in an attempt to stamp out speculative activity. Margin loans spur stocks to rise and fall quickly.

Still "the direction may be irreversible," Mr. Chan wrote in a note Thursday. "Informal activities will turn back to offline and be underground, only to serve big individual clients as they were before."

Investor's have been unnerved by Shanghai's irregular intraday trading, which some analysts put down to government intervention in the market. On Wednesday, the index surged in the last hour of trading, which likely enticed more local investors to chase the gains. Chinese authorities don't disclose their pace of buying in the market, or the total amount that they have bought up in stocks.

In South Korea, shares of Samsung Electronics Co. were down 1.7% after the firm said net profit for the second quarter fell 8%. Sales for the company's flagship Galaxy S6 smartphone fell short of market expectations and hurt profits.

Oil prices rose Wednesday in the U.S. on unexpected declines in U.S. crude-oil supplies and production. Prices have slumped this month on renewed fears about a global glut and China's faltering demand. Crude oil futures were up two cents at $48.81 a barrel.

Gold prices rose sharply after the Federal Reserve's statement, but quickly gave up gains. Gold rallied as high as $1,100.90 a troy ounce in aftermarket trading Wednesday as is currently at $1,097.20 in Asia.

Gold prices had sank to five-year lows in recent weeks amid expectations for a rate increase, which could incite investors to move to higher-yielding assets.

Write to Chao Deng at Chao.Deng@wsj.com