Four workers in Japan have died after being struck by a train at Shin-Kanuma Station, north of Tokyo, authorities say.

The collision happened around 10:46 local time (01:46 BST) on Thursday while the workers were spraying herbicide, said Tobu Railway, the operator of the line.

Police are investigating if safety guidelines were followed when the accident happened, Tobu Railway officials told a press conference.

Train service was suspended on the Tobu Nikko Line due to the accident, according to Tobu Railway.

A passenger on the train told Japanese public broadcaster NHK that they heard a "strange noise" before the train made an emergency stop.

He said passengers were stuck on the train for a while as staff announced that they were investigating the noise.

Fatal train accidents are rare in Japan, which relies on a sprawling railway network.

The train involved in Thursday's incident was a limited express train, according to NHK. These are the second-fastest trains in Japan, after the Shinkansen or bullet train.

The fatalities, who were in their 50s and 60s, were among a team of ten working at the site on Thursday, railway officials said.

The team also included a supervisor and three lookouts tasked with alerting workers to incoming trains.

The lookouts generally use whistles and microphones to alert the workers, while waving a yellow flag at the train driver.

When asked repeatedly if anyone had been looking out for trains ahead of the accident, the officials did not give clear answers.

A Tobu Railway representative told the BBC earlier that the "usual lookout system was operating as normal".

"When a train approaches, a lookout waves a flag and, once the driver acknowledges it, sounds the horn," he said.

"We are currently investigating why the accident occurred despite this."

Tobu Railway general manager Takao Suzuki said the company offered "our deepest condolences to those who lost their lives and heartfelt apologies to their families".

"We also deeply apologise for the inconvenience caused to all those involved and to our customers," he said.