A schoolgirl and a 39-year-old man were killed and 15 other young girls injured when a knifeman attacked a group of children waiting for a bus to primary school outside Tokyo on Tuesday.

The apparently random attack took place in the city of Kawasaki, just south of the capital, as the children waited with their parents at a bus stop at about 7.45am.

The suspect, a man in his 50s, was detained at the scene and later died from self-inflicted injuries to his shoulder and neck, national broadcaster NHK reported.

Kiyoshi Matsuda, deputy director of the Nippon Medical School Musashi Kosugi Hospital, told reporters that the 11-year-old schoolgirl and a 39-year-old man had succumbed to their injuries.

Hanako Kuribayashi, who was in the sixth grade, and foreign ministry official Satoshi Oyama, who is believed to be the parent of another child, both died, police said later.

Another woman was severely injured along with the 15 other schoolgirls who were hurt, NHK said.

Eyewitnesses report seeing the man, described as being in his 40s or 50s, stabbing the girls with knives in both hands as they waited in line for their school bus.

The girls, aged between 6 and 12, were students at a private Catholic school.

Rescuers work at the scene of an attack in Kawasaki, near Tokyo credit: AP

"I saw a man holding a knife... I couldn't see clearly, but he apparently stabbed himself in the neck," one eyewitness told NHK.

Police have recovered two knives at the scene, but there have been no reports about a motive for the attack. Police are also still trying to identify the suspect.

"I heard screaming, then I saw a man standing with a knife in each hand," NHK quoted an unidentified witness as saying. "Then he crumbled to the ground."

Images broadcast on Japanese television show police cars, ambulances and fire engines blocking the narrow streets close to the bus stop, in a residential district close to Noborito Station, with large, orange tents set up over the crime scene. Roads around the site have been blocked off.

Police forensic experts are seen at the crime scene where a man stabbed 19 people, including children in Kawasaki credit: AFP

"I heard the sound of lots of ambulances and I saw a man lying near a bus stop bleeding," a male eyewitness, who was not identified, told NHK.

"There is another bus stop near the elementary school and I also saw elementary schoolchildren lying on the ground... It's a quiet neighbourhood, it's scary to see this kind of thing happen," he added.

Shinzo Abe, the Japanese Prime Minister, voiced "strong anger" over what he described as a "harrowing" attack.

"It is a very harrowing case. I feel strong anger. I offer my heartfelt condolences to the victims and hope the injured recover quickly," Mr Abe said in a televised reaction, his first since the attack.

US President Donald Trump, who is visiting the country, said Americans "stand with the people of Japan" after the mass stabbing.

The attack occurred during the busy early morning commute as workers headed to their offices and children to school in Kawasaki, a city south of Tokyo. credit: AFP

Standing aboard a Japanese military ship, he offered "prayers and sympathy to the victims of the stabbing attack", adding that "all Americans stand with the people of Japan and grieve for the victims and for their families".

Japan has one of the lowest rates of violent crime in the developed world and mass attacks are extremely rare.

In 2018, a man was arrested in central Japan after stabbing one person to death and injuring two others aboard a bullet train, an attack that prompted new security measures on the famed rail service.

And in 2016, a man stabbed 19 people to death in a disability centre south of Tokyo in what he described as a mission to rid the world of people with mental illness.