South Korea’s Kosdaq index of mainly small-cap technology stocks slumped on Monday, triggering the first trading suspension in more than three years, as investors sold on rising trade tensions with Japan.

The gauge, comprising 1,336 stocks of the nation’s small- and medium-sized companies, slid more than 5% before the Korea Exchange halted program trading for five minutes. The index recently dropped 7.1%. The index has slipped nearly 15% this year, the worst-performing index in Asian major markets.

Investors “have lost trust” in the nation’s biotech and healthcare firms, many of which are listed on the Kosdaq, said Heo Pil-Seok, chief executive officer at Midas International Asset Management. After rallies stretching over years, there has been a spate of botched clinical trials and canceled licenses, Heo said.

Korea’s disputes with Japan are also triggering a bigger outflow from the Kosdaq than from the benchmark Kospi, he said.

“Both the governments of South Korea and Japan are ratcheting up tensions instead of resolving the dispute,” Heo said. “There’s concern that the feud with Japan would be negative more to small- and medium-sized firms, rather than conglomerates.”