* Uniper shares hit lowest level since November 2020

* Shares in parent Fortum hit 14-month low

* Companies employ 7,000 staff in Russia (Recasts with context, updates shares)

FRANKFURT/HELSINKI, Feb 24 (Reuters) - Shares in German utility Uniper and largest shareholder Fortum , which both run substantial businesses in Russia, plummeted on Thursday following Moscow's move to invade Ukraine.

Between them, the companies employ 7,000 staff in Russia, where they operate a dozen power plants, many fuelled by gas, to supply local communities and industries.

Shares in Uniper fell as much as a fifth to their lowest level in more than 15 months, while Fortum, which owns 76% in Uniper, fell up to 10.4% to a 14-month low.

Russian forces invaded Ukraine on Thursday in a massed assault by land, sea and air, the biggest attack by one state against another in Europe since World War Two.

"Energy production in Russia has not been sanctioned, and therefore our operations there have not been directly impacted," Fortum said in a statement. It said it was monitoring decisions on sanctions and counter-sanctions.

Uniper owns a majority in Russian utility Unipro and is one of the financial backers of the Nord Stream 2 gas pipeline project whose certification German Chancellor Olaf Scholz put on hold on Tuesday in response to the Ukraine crisis.

Uniper said on Wednesday it was assessing whether Berlin's suspension of the Nord Stream 2 pipeline would cause impairments on its 1 billion euro ($1.1 billion) exposure to the project.

"We very much regret the escalation of the situation with Russia's attack on Ukraine and are following the situation with utmost concern," Uniper said in a statement.

"We are in the business of providing security of supply of energy and our customers depend on us for power and heat. This is the case also in Russia."

($1 = 0.8890 euros)

(Reporting by Christoph Steitz and Essi Lehto, editing by Kirsti Knolle, Barbara Lewis and Marguerita Choy)