South Korea's KOSPI returned above the 7,000 level for the first time in four sessions on a surge in U.S. semiconductor shares and buying by foreign and institutional investors. As gains widened rapidly, the main board market triggered a buy sidecar for a second straight day, following the previous session's activation, temporarily halting program buy orders.

According to the Korea Exchange, the KOSPI was up 383.00 points, or 5.68 percent, at 7,130.95 as of 9:04 a.m. The index opened up 304.14 points, or 4.51 percent, at 7,052.09 and moved above 7,100 soon after the open. It marked the first time in four sessions that the KOSPI regained the 7,000 level during the session.

With gains widening, a buy sidecar was triggered in the main board market at 9:06 a.m. It was activated for a second consecutive trading day, following the previous session.

At the time of activation, the nearest-month KOSPI200 futures stood at 1,139.30, up 58.46 points, or 5.40 percent, from the base price of 1,080.84. The buy sidecar halted the effectiveness of program buy orders for 5 minutes.

It was the 20th buy sidecar this year. Including sell sidecars, it was the 40th sidecar triggered this year in the main board market.

In the main board market, foreign investors posted net purchases of 601.8 billion won and institutions bought a net 296.7 billion won. Retail investors sold a net 306.5 billion won.

Most top stocks by market capitalisation rose. Samsung Electronics gained 15,000 won, or 5.79 percent, to 274,000 won.

SK Hynix rose 154,000 won, or 8.39 percent, to 1,990,000 won, nearing 2,000,000 won. SK Square jumped 10.30 percent and Samsung Electro-Mechanics surged 10.23 percent.

Elsewhere, Hyundai Motor rose 5.39 percent and Samsung Life Insurance gained 6.96 percent. LG Energy Solution added 2.68 percent, Samsung Biologics rose 1.86 percent and KB Financial Group climbed 2.53 percent.

The Kosdaq was up 23.45 points, or 3.11 percent, at 776.79.

In the Seoul foreign exchange market, the won was trading at 1,481.00 per dollar, up 1.50 won from the previous session.

The domestic market's strength was attributed to a broad rally in semiconductor stocks in the U.S. market the previous day. Micron rose 12.17 percent, AMD gained 8.11 percent, Broadcom added 2.21 percent and Nvidia rose 1.97 percent. The Philadelphia Semiconductor Index also climbed 5.21 percent.

On the back of that, the Dow Jones Industrial Average rose 0.74 percent, the Standard & Poor's 500 index gained 0.89 percent and the Nasdaq index climbed 1.29 percent.

Han Ji-young (한지영), an analyst at Kiwoom Securities, said a broad surge in U.S. semiconductor shares, strength in KOSPI200 overnight futures and expectations for domestic companies' second-quarter earnings would drive the local market higher. But she said the possibility of greater intraday volatility remains due to a high volatility index and an increase in leveraged single-stock trading.