HELSINKI (AFP) - A planned strike by Finnish airport security staff could cause long lines at the Nordic country's main Helsinki-Vantaa airport, airport service company Finavia said Wednesday.

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Airport security staff are set to go on a one-day strike Friday in a sign of solidarity with security guards currently locked in a labour dispute.

"Security checks will be handled by Finavia security personnel and foremen," Finavia said in a statement, adding "around one third" of the normal number of staff would be at the airport to conduct security checks.

"This will cause considerable queues and slowness in security checks," it said, urging passengers to arrive early for their flights.

All scheduled flights will be flown as planned despite the planned strike, Reijo Tasanen, Finavia senior vice president, told AFP.

"Flight safety will in no way be compromised," Tasanen said, adding all security staff expected on duty Friday were trained professionals. "Security checks will be done as thoroughly as usual during the strike."

Airport security staff said Tuesday they would go on a one-day support strike to stand with security guards, whose PAM union is currently negotiating a collective labour deal.

Labour talks for the security services sector are expected to continue Thursday evening, according to PAM, which on Tuesday warned of further possible strikes by security guards from Wednesday, April 28, to Saturday, May 1.

Friday's strike is due to begin at 6:00 am (0300 GMT) and to end 24 hours later.

Jyrki Sinkkonen, secretary for collective agreements at PAM, told AFP Friday's strike was "very likely" to go ahead as talks thus far had "not even properly addressed salaries".