Algeria’s state energy firm Sonatrach has called on international engineering firms to bid on four major petrochemical plants worth a total of up to $6 billion, a report said.

The firms selected will carry out construction work on the four refineries, Oman Observer reported, citing a source at Sonatrach.

The plants are located in Tiaret, Hassi Messaoud and two in Skikda, including a fuel oil cracking plant, and another Nafta processing plant.

The plants in Tiaret and Hassi Messaoud will have 5 million tonnes capacity each, the report quoted the source.