Son Wan-Ho led South Korea in dashing the Chinese men's dream of reclaiming the Thomas Cup late Thursday, upsetting the tournament favourites in a shocking 3-1 quarter-final upset in Kunshan.

China were forced to fight back from a deficit early at the world badminton championship after top ranked Chen Long dropped a nail-biting one hour and 27 minute match to ninth ranked Son.

"He did well and was more patient today," Chen told reporters following the 12-21, 21-16, 15-21 loss. "I didn't do well because I think too much."

China's troubles only deepened when South Korea's Lee Yong-Dae and Yoo Yeon-Seong unleashed repeated blitzing attacks to beat Fu Haifeng and Zhang Nan in a three-game thriller.

Badminton legend Lin Dan briefly lifted the Chinese fans' spirits with a 21-10, 21-15 win.

But momentum appeared firmly against the home team. South Korea's Kim Gi-Jung and Kim Sa-Rang made it official and clinched a spot in the semi-finals with a straight sets triumph in the face of dogged resistance from China's Li Junhui and Zheng Siwei.

"Our players tried their best, but they lost. It's unfortunate," said badminton fan Hai Yanwong, as fellow partisans hissed and shouted at the result -- with one weeping fan escorted out by security.

South Korea will face Indonesia in the semi-finals on Friday.

China's women prevail

In the women's Uber Cup, China appeared indomitable as they marched into the semi-finals, pummelling Taiwan 3-0.

World number three Li Xuerui led the charge out of the gate and breezed past Taiwan's Pai Yu-po 21-14, 21-17.

Wang Shixian kept up the momentum, walloping Hsu Ya-ching 21-16, 21-12, while doubles duo Tian Qing and Zhao Yunlei completed the sweep in straight sets in 32 minutes.

In earlier play, Lee Chong Wei led Malaysia into the Thomas Cup semis, while there was Uber Cup heartbreak for Ratchanok Intanon as Thailand crashed out against India.

Lee, the world number two, kick-started Malaysia's effort with whipping overheads and delicate, cross-court drop shots as he beat Taiwan's Chou Tien-chen 21-18, 21-18.

Afterwards Lee brushed off suggestions that pressure was mounting on Malaysia's men as they seek to end their 24-year drought at the Thomas Cup.

"A win for today and then I'll focus on tomorrow," said Lee, who is eyeing a maiden Olympic title in Rio de Janeiro in August.

Iskandar Zulkarnain Zainuddin thrashed Hsu Jen-hao before doubles team Koo Kien Keat and Tan Boon Heong won the decisive match as Malaysia clinched it 3-1.

Malaysia will face the tournament's second seed Denmark in the semi-finals, after the Danes earned a dramatic 3-2 win over Japan late on Thursday.

Indonesia also reached the Thomas Cup semis thanks to strong singles performances from Tommy Sugiarto and Jonatan Christie as they sent Hong Kong packing 3-1.

On the women's side, second-ranked Ratchanok utilised her crafty backhand and sliced forehands as she beat Olympic bronze medallist Saina Nehwal 21-19, 21-12.

But Pusarla V. Sindhu made short work of Busanan Ongbumrungphan and Gadde Ruthvika Shivani beat Nitchadon Jindapol 21-16, 21-18 as India clinched it 3-1.

"We thought we had less of a chance after Saina losing," said Shivani. "Our first step was to beat the Thai team... so we'll decide what to do (in the semis) now."

India will square off with tournament favourites China in the semi-finals.