OSAKA -- Four men assaulted and tied up four Taiwanese in an Osaka building early Monday then stole 3.5 million yen and $500 in cash and other valuables from them, police said.

The attack occurred at around 1:50 a.m. in two third-floor rooms of the Miyazaki Building in Chuo Ward after the assailants broke into the building, police said. Three of the Taiwanese -- two men and two women -- were injured.

According to police, Taiwanese tourists sometimes use the third floor of the building as a lodging facility and the assailants, who reportedly spoke Chinese, appeared to be familiar with the building.

Among the four victims were 62-year-old Kuo Lulien-tui, a buyer of Japanese clothes, and Hu Heng-hao, 25, a computer programmer, police said.