Mills including Torras Motril, Holmen Paper Madrid, SCA Papel Higiénico, SAICA I Y II Aragon and Smurfit Jaen are affected by the 24-hour strike, with another 24-hour strike planned for 3 March.
Dick Blin, pulp and paper officer at the International Federation of Chemical, Energy, Mine and General Workers' Unions, said unions and employers' association ASPAPEL met yesterday to avert the strike, but to no avail.
He said: "The situation is rather dire since unions spent all of 2010 in talks for wage increases and got nowhere on a 2010 collective agreement.
"Workers, obviously, are frustrated because they've seen no 2010 increase."
He added that the UK, along with other markets, will be affected by the strike.
"There's been a good turnout today. The slump in the Spanish economy generally has been a factor behind the strikes."
He added that workers at one of three Kimberly Clark mills (Salamansa) have struck.
Other mills affected include Papertech Navarra (100% of workers on strike), Ibertisu Navarra (95%), Troncheti Aragon (100%), Newart Catalana (100%), Goma Camp La Riba (100%), Vilaver (100%), Torras San Joan (90%) and Clariana Castellón (100%).
In total, 17,500 workers involved in the action are based in 120 sites across Spain.
Unite national officer Peter Ellis said he was concerned that employers in another European country are going along with a no pay increase situation.
He added that the impact on the UK market is yet to be seen.
