Super featherweight Shigetoshi Kotari and lightweight Hiromasa Urakawa, both 28, fought on the same card at Tokyo's Korakuen Hall on August 2 and died days later following brain surgery.

Kotari died on Friday and Urakawa on Saturday after being injured in their fights, Japanese media said. Both 28-year-old boxers underwent operations for subdural haematoma, or bleeding inside the skull, the reports said.

"We extend our deepest condolences to the families, friends, and the Japanese boxing community during this incredibly difficult time," the World Boxing Organization said in a statement on Saturday about Urakawa, who had lost to Yoji Saito in a knockout.

Kotari died as a result of the injury he sustained while fighting Yamato Hata to a draw in 12 rounds, the World Boxing Council said on Friday.

"The WBC and its President, Mauricio Sulaiman, deeply mourn this irreparable loss and wish his family and friends strength during this difficult time," the WBC said in a statement.

The Japan Boxing Commission (JBC), gym owners and other boxing officials are under pressure to act and will hold an emergency meeting on Tuesday.

They are also expected to have talks about safety next month, local media said.

"We are acutely aware of our responsibility as the manager of the sport," Tsuyoshi Yasukochi, secretary-general of the JBC, told reporters on Sunday.

"We will take whatever measures we can."

Japanese media highlighted the risks of fighters dehydrating to lose weight rapidly before weigh-ins.

"Dehydration makes the brain more susceptible to bleeding," the Asahi Shimbun newspaper said.

That is one of the issues the JBC plans to discuss with trainers.

"They want to hear from gym officials who work closely with the athletes about such items as weight loss methods and pre-bout conditioning, which may be causally related (to fatalities)," the Nikkan Sports newspaper said.

In one immediate measure, the commission has decided to reduce all Oriental and Pacific Boxing Federation title bouts to 10 rounds from 12.

"The offensive power of Japanese boxing today is tremendous," Yasukochi was quoted by the Asahi Shimbun as telling reporters.

"We have more and more boxers who are able to start exchanges of fierce blows from the first round. Maybe 12 rounds can be dangerous."