A strike by railway ticketing staff has forced the cancellation of most national and international train services in Portugal.

National rail company Comboios de Portugal said only about 10 percent of trains ran as scheduled Monday as ticket sellers and inspectors walked off the job for 24 hours.

The company predicts delays and cancellations through the end of June due to an overtime ban by all staff and occasional daylong strikes by train engineers.

Workers are angry that an agreement on working conditions they signed with the company in April still has not come into force.