Posco jumped 9 percent this week to 140,000 won after its board decided on Wednesday to raise dividends and cancel 21 percent of the company's shares.
The steelmaker said Thursday that profit tripled in the second quarter to its highest in three years because of rising demand from builders and carmakers in South Korea and China.
Kookmin Bank, the nation's largest lender, gained 5.5 percent to 42,000 won this week on optimism earnings may improve in the second half as fewer people default on credit-card payments.
South Korea's Financial Supervisory Service said in a report that the combined ratio of payments overdue for more than a month at the nation's nine major credit-card companies declined to 9.7 percent in June from a record 11.7 percent in May.
Taiwan, Hong Kong
Companies in Taiwan with business links to China advanced after a Chinese-language newspaper reported over the weekend that China's government proposed a free-trade accord with Taiwan. Under the free-trade agreement, businesses in Taiwan will find it easier to start up businesses in China.
Hon Hai Precision, a computer-cable connector maker with factories in China, gained 8.1 percent to NT$161 this week.
Quanta Computer Inc, which makes notebook computers near Shanghai for clients such as the US-based Dell Inc, jumped 11 percent to NT$87.5.
China Mobile, China's biggest mobile-phone company, fell 6 percent to HK$19.75. China Unicom Ltd, Hong Kong's No. 2 cell-phone company, ended the week 5.3 percent lower at HK$5.35.
The shares fell after Tim Long, an analyst at Credit Suisse First Boston, cut his rating to "underperform" from "neutral" on Motorola, the world's second-largest maker of mobile phones, saying the company may not meet this year's earnings estimates.