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Chinatopix via The Associated Press
Investors react as they check stock prices in a brokerage house in Fuyang in central China's Anhui province Friday, June 26, 2015. Chinese stocks plunged on Friday as panicked investors rushed to sell over fears that an extended bull market was coming to an end.

HONG KONG — Chinese stocks plunged on Friday as panicked investors rushed to sell over fears that an extended bull market was coming to an end. Other world benchmarks fell as a standoff between Greece and its international creditors threatened to drag into the weekend.

KEEPING SCORE: European stocks opened lower, with France's CAC 40 down 0.5 percent to 5,015.19. Germany's DAX fell 0.5 percent to 11,418.47. Britain's FTSE 100 shed 0.9 percent to 6,745.86. U.S. stocks were poised for an uneven open. Dow futures were up less than 0.1 percent to 17,817.00. Broader S&P 500 futures dipped less than 0.1 percent to 2,093.50.

SHANGHAI SLUMP: After a sizzling rally that more than doubled Shanghai's benchmark index over the past year, investors are now heading for the exit. One factor appears to be authorities tightening rules on margin financing, which involves using borrowed money to buy stocks. The market's drop may also be exacerbated by the herd mentality of retail investors, who play an outsize role in China's markets, or by margin investors being forced to sell off to meet margin calls.

ANALYST INSIGHT: "Although I continue to be optimistic about the longer-term trend of the China markets, it's clear that we are in a sharp correction phase," said Bernard Aw of IG Markets in Singapore. He said up until Thursday, $1.2 trillion had been wiped off of China's equity markets since they peaked June 14 at $10 trillion.

ASIA SCORECARD: The Shanghai Composite Index in mainland China plunged 7.4 percent to close at 4,192.87, bringing its losses for the week to 12.4 percent. The smaller Shenzhen Composite Index tumbled 7.9 percent to 2,502.96. Hong Kong's Hang Seng dropped 1.8 percent to 26,663.87. Asian benchmarks outside of China were more muted. Japan's benchmark Nikkei 225 index lost 0.3 percent to 20,706.15 while South Korea's Kospi gained 0.3 percent to 2,090.26. Australia's S&P/ASX 200 shed 1.5 percent to 5,545.90.

GREEK TALKS: Global investors are watching closely as Greek debt talks go down to the wire. On Thursday, a key meeting of eurozone finance ministers on Greece's rescue package broke up without agreement, intensifying doubts about whether Athens can repay a 1.6 billion euro ($1.8 billion) debt to the International Monetary Fund due Tuesday. A new meeting is tentatively scheduled for Saturday. Creditors will not free up billions in bailout money until there's an agreement on a drastic tax and austerity reform package for the Mediterranean nation.

ENERGY: Benchmark U.S. crude oil fell 23 cents to $59.47 a barrel in electronic trading on the New York Mercantile Exchange. The contract dropped 57 cents to close at $59.70 a barrel in New York on Thursday. Brent crude, a benchmark for international oils used by many U.S. refineries, fell 14 cents to $63.06 in London.

CURRENCIES: The euro rose to $1.1210 from $1.1205 in the previous trading session. The dollar weakened to 123.39 yen from 123.62 yen.