Asia extended a selloff in global equities on Thursday, as heightened concerns about world economic growth sent Japanese stocks tumbling and U.S. MSCI’s broadest index of Asia-Pacific shares outside Japan extended early losses and was down 0.6 percent while Japan’s Nikkei stock average (.N225) tumbled 2.2 percent and touched a 4-1/2-month low. “It’s clear that people are avoiding risks,” said Takatoshi Itoshima, chief portfolio manager at Commons Asset Management.