The man arrested on board a Thalys train at Rotterdam station on Friday morning, causing a massive security scare, was unarmed and his rucksack only contained personal possessions.

The man had jumped onto the train as it was about to leave and locked himself in a toilet. It is not yet clear how the security services were alerted, but according to some reports, passengers had become suspicious.

Police evacuated the train and sealed off part of the station, most of which has now been reopened. However, train services to and from Rotterdam will take some time to return to normal, Dutch railway company NS said.

The man was eventually taken away on a stretcher because, police said, he did not feel well and had been hyperventilating.

Police said they had not yet determined why the man locked himself in the toilet or if he was simply trying to avoid paying a fare.

Meanwhile, a suspicious bag left on a train travelling from Brussels to Amsterdam has been blown up on Antwerp station.

Belgian police said they did not want to take any chances following the Thalys scare at Rotterdam, news agency ANP reports.