Korea's selloff deepened past 10 percent, the worst level since April, while American futures barely moved

South Korea's stock market kept falling on Tuesday afternoon in Seoul, well past the level that had already stopped trading once that morning.

The KOSPI was down about 10.5 percent at 6,051.19 by midday, its lowest since April, the Associated Press reported. Earlier in the session the Korea Exchange had triggered a Level 1 circuit breaker at 10:13 a.m. local time and halted trading for 20 minutes, with the index then down 8.02 percent at 6,213.51. Korean rules set the next index-wide halt at a 15 percent decline, so the fall from 8 percent to 10 percent did not stop trading a second time.

The two companies at the centre of it fell further than the index. Samsung Electronics was down 12 percent and SK Hynix down 12.7 percent, according to the AP, against declines of 9.45 percent and 11.1 percent earlier in the day. Between them the two firms account for roughly half the capitalisation of the Korean market, which is why a problem in one sector reads as an index-wide crash in Seoul and not anywhere else.

Elsewhere in Asia the picture was uneven rather than uniform. Japan's Nikkei 225 fell about 3.8 percent to 62,448.56 and Taiwan's Taiex fell 3.9 percent, both chip-heavy markets. Hong Kong's Hang Seng was down 0.1 percent at 25,178.21 and Australia's S&P/ASX 200 was up 0.6 percent at 8,944.40.

The catalyst analysts pointed to remained Monday's listing in Shanghai. ChangXin Memory Technologies, China's largest producer of DRAM, raised about $8.6 billion on the STAR Market in the largest semiconductor offering ever done on the mainland, and its shares rose 466 percent on their first day of trading. Analysts quoted by the AP tied the selling to concern that Chinese chipmakers and artificial intelligence startups will erode the gains of established global technology companies.

American futures did not follow Asia down. S&P 500 futures were quoted at 7,429.75, down 0.25 percent, and Nasdaq 100 futures at 27,966.25, down 0.79 percent, in the hours before the New York open.

The Federal Open Market Committee convenes on Tuesday for a two-day meeting, with a decision due Wednesday.

A note on sourcing and timing. Korean and Japanese markets were still open as this was written, so those figures are intraday and will move before the close. The index levels, the two Korean share prices and the regional index figures come from the Associated Press report credited above. The Nikkei level and the two American futures quotes were taken directly from market data at about 1 a.m. Eastern time. The circuit breaker time and the 8.02 percent level come from the Korea JoongAng Daily's earlier report, carried in this site's item on the same session. The Korea Exchange publishes its circuit breaker record through a session-based portal rather than a fixed public address, so there is no primary document linked here.