Russia's Sibur and TAIF will combine their petrochemical businesses to create one of world's top five producers of polyolefin and rubber products, they said on Friday.

Russian energy companies, led by privately owned Sibur, have increasingly been shifting their focus to petrochemicals in a drive to capitalise on the fast-growing sector and offset the volatile market for crude oil exports.

"This combination will make the new company's petrochemical operations more competitive in the global market, improve its resilience to market fluctuations, and also unlock further growth potential of Russia's petrochemical industry," the companies said in a statement.

TAIF said the deal would help TAIF Group accelerate key projects in its 2030 strategic development programme that will see more than 1.5 trillion roubles ($20 billion) of investments over the next 10 years.

Sibur, the largest petrochemicals producer in eastern Europe, said existing TAIF shareholders would receive a 15% stake in PJSC Sibur Holding in exchange for transferring a controlling interest in TAIF's group of petrochemical and energy firms.

The remaining stake in TAIF can be subsequently purchased by the combined company.