The maintenance works will be carried out with maximum involvement of the company's workforce and with minimum investments, Petrokemija said in a filing to the Zagreb bourse.
The production facilities will successively be brought offline from the beginning of January and the company expects them to be fully operational as of early February.
Petrokemija said it has ensured sufficient supplies of mineral fertilizers as well as production at plants not being overhauled in order to meet the anticipated demand on the domestic and foreign markets.
The company's shares were trading down 5.41% at 26.21 kuna ($4.2/3.4 euro) by 1209 CET on the Zagreb Stock Exchange on Friday.
Kutina-based Petrokemija employs around 2,300.
(1 euro=7.6666 Croatian kuna)