Russian chemicals maker Acron Group increased its stake in Polish state-controlled rival Grupa Azoty SA to 20%, raising pressure on the Polish government for closer cooperation between the two companies.

Acron launched a hostile takeover bid for the Polish state-controlled company in 2012 but its plan was thwarted by the government, which instead of selling its stake responded with changes that prohibit Acron from taking over Grupa Azoty.

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