Another letter bomb has been found and made safe by the bomb squad, this time at a software company in Leusden, broadcaster NOS reports.

The letter, delivered to tech company Unisys which specialises in payment traffic systems, aroused suspicion after a police warning on Wednesday when two letter bombs exploded in Amsterdam and Kerkrade. No one was hurt in those explosions.

Police also showed a photograph of one of the packages, typically a bulky white envelope with two stamps and a printed address. The letters were sent by a blackmailer demanding to be paid in bitcoins.

In early January a number of letter bombs were sent to hotels, petrol stations and garages and a real estate office. All were preceded by a blackmail letter demanding payment.