BEIJING (AP) _ Death threats against Japanese in China have led to the tightening of security against a group calling itself the ''Blood-Bright Dare to Die Squad,'' Japanese residents in Beijing said today.

In letters sent recently to Japanese businesses in China accusing Japan of plotting an economic invasion, the group threatened to kill two ''Japanese pirates'' - businessmen or tourists - a week beginning today.

The Japanese Embassy said no special measures were planned in addition to earlier warnings to its nationals to take precautions such as varying their routes to work and staying indoors at night.

But an official at Japan Airlines, which received one of the death threats, and other businessmen working in hotels throughout the city said security had been increased by local authorities.

''We haven't done anything special ourselves, but stricter security measures are being taken by the Public Security Office at the Beijing Airport,'' said Japan Airlines manager Shigeki Suetsugu.

The Jinglun Hotel, where JAL's ticket and reservations office is located, also has employed additional undercover and uniformed guards to improve security, Suetsugu said.

About 230 Japanese businessmen living and working at the Minzu Hotel in Beijing met with hotel staff to plan extra security precautions, including mandatory registration of visitors in the evenings, said Toshimi Inoue, manager of a trading company with offices in the hotel.

''All the hotels are looking out for the Japanese,'' Inoue said. ''Of course, we don't really expect anything to happen, but it's better to take precautions,'' he added.

Almost all Japanese living in China went home following the crushing of student-led pro-democracy protests in June, but most Japanese businessmen have since returned.

While Japanese tourists are staying away, most businessmen are going ahead with business as usual, said Kenji Ishii of the Japan Association for Promotion of International Trade.

''You can't spend all day worrying. After all, there are extremists in Japan, too.'' said Inoue, who has managed a trading firm in Beijing for four years.

''The protests last spring seem to have brought some of those types (like the Blood-Bright Dare to Die Squad) out into the open here in China, too,'' he said.

Some Japanese say the death threats have cast a pall over living and working in China.

''It would be a lie to say I'm not worried. It's creepy,'' said Japan Airlines manager Shigeki Suetsugu.

''We don't expect anything to happen, but the threats make it impossible for us to move around freely. It makes life here rather grim,'' he said.