An estimated 200 Posti employees gathered on Tuesday for a demonstration in Helsinki on the second day of a national postal strike.
They marched from the Ilmala neighbourhood to Posti headquarters in nearby Pasila. The demonstration was called by the Finnish Post and Logistics Union (PAU), with activists arriving from around the country.
Meanwhile the Trade Union for the Public and Welfare Sectors (JHL) has announced a sympathy strike and the Aviation Union (IAU) says it will continue its own support measures as long as the postal strike lasts, which could be a month or more.
JHL locomotive engineers will decide on Thursday whether to walk out in support of the postal workers.
The JHL walkout would close down freight train rail yards next Tuesday, 19 November, with train maintenance workers joining the action the following day. The walkouts would not affect passenger train traffic.
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The unions say they want to help accelerate PAU's negotiations with the employers' group Palta over working contracts for some of the majority-state-owned company's staff.
JHL: Posti moves "nasty and immoral"
"Posti's management is trying in a completely nasty, immoral way to achieve profit by trampling on collective agreements," JHL president Päivi Niemi-Laine said in a statement on Tuesday.
IAU president Juhani Haapasaari said that the aviation union is prepared to extend its sympathy strike as long as PAU members are off the job. The IAU had originally planned for its job action to last until 24 November.
The union has stopped all support functions for Posti handling at the nation's airports, which has effectively halted international air mail deliveries.