Oslo  - Striking Norwegian civil aviation employees caused a further six Norwegian airports to close Tuesday, bringing the total of airport closures to 12 and impacting some 31,000 passengers.

The country's main airport, Oslo's Gardermoen airport, remained open but flights were also cancelled Tuesday affecting some 8,000 passengers, airport officials said.

Among the airports closed Tuesday was Sola that serves the west coast city of Stavanger which usually has some 11,000 passengers per day.

Some 400 civil aviation employees were on strike. Their absence has forced airport closures due to insufficient staff to respond to possible emergencies or fires.

The civil aviation authority, Avinor, and unions have not held any meetings since mediation efforts failed early Friday.

Avinor spokesman Ove Narvesen said, "We can not say anything about when such contact will be re-established."

"Avinor has the means to end the strike," Stein Erik Syrstad, spokesman for the trade union confederation LO Stat that organizes the government-hired employees, told Norwegian news agency NTB.

Passengers were advised to consult websites operated by the respective airlines over cancellations and if possible look into alternative means of travel. (dpa)