MOSCOW, Feb 28 (Reuters) - International energy major BP has opted to leave Russia after Western countries imposed severe sanctions on its companies and individuals following Moscow's military attack on Ukraine.

BP, the biggest foreign investor in Russia, said it was abandoning its stake in state oil company Rosneft at a cost of up to $25 billion, shrinking its oil and gas reserves in half.

Following are some facts about exposure of Western oil and gas companies to Russia, which calls its actions in Ukraine a "special operation":

BP

The British oil major has a 19.75% stake in Rosneft, headed by Igor Sechin, a long-standing ally of President Vladimir Putin. Rosneft accounted for a third of BP's oil and gas output in 2021.

BASF

The German chemicals maker co-owns Wintershall Dea - one of the financial backers of the suspended Nord Stream 2 gas pipeline - with Russian billionaire Mikhail Fridman's LetterOne investor group. BASF also says it generates 1% of group sales from Russia.

Wintershall Dea and Gazprom jointly work at Achimov Development gas producing project.

ENGIE

The French gas utility is one of five co-financiers of Gazprom's Nord Stream 2 and has a stake in Nord Stream 1 operating pipeline along with Wintershall Dea, E.ON and Gasunie.

ENI

The Italian company and Gazprom have 50% each in the Blue Stream gas pipeline to Turkey.

EQUINOR

The energy group, which is majority owned by the Norwegian state, said on Monday it will start divesting its joint ventures in Russia. It has minority stakes in three Russian oilfields.

- Norway's sovereign wealth fund, the world's largest, will also divest its Russian assets, worth around 25 billion Norwegian crowns ($2.80 billion).

EXXONMOBIL

The international oil major's key asset in Russia is the Sakhalin-1 oil and gas producing project in the Pacific. ExxonMobil also markets petrochemical products in Russia that are used by local industries, according to its website.

An ExxonMobil affiliate has a 7.5% interest in the Caspian Pipeline Consortium (CPC), which exports oil from Kazakhstan via Russian Black Sea port of Novorossiisk.

The company had exited a number of joint ventures in Russia following sanctions, imposed after Moscow's annexation of Crimea in 2014.

OMV

The oil and gas company is one of the five financial backers of Nord Stream 2 and is Austria's main importer of Russian gas. It has a 24.99% stake in Russian gas field Yuzhno-Russkoye.

SHELL

The Anglo-Dutch oil company is one of the biggest direct foreign investors in the Russian economy. It owns 27.5% of the Sakhali-2 liquefied natural gas project, which has an annual capacity of 11 million tonnes and is operated by Gazprom . It's one of the five co-financiers of Nord Stream 2.

Shell also has interests in the Salym Petroleum oil project with Gazprom Neft and a venture for hydrocarbon development at Gydan Arctic peninsular.

TOTALENERGIES

The French company holds a 19.4% stake in Novatek , Russia's largest producer of liquefied natural gas (LNG). It has a 20% stake in the Yamal LNG project as well as a 10% interest in Arctic LNG 2, scheduled to start production next year.

The company also holds a 49% stake in the Terneftegas joint venture, which develops the Termokarstovoye onshore gas and condensate, and a 20% interest in the onshore Kharyaga oil field, its website shows. It has acquired 10% in LNG transhipment hubs in Murmansk and Kamchatka.

UNIPER

The German utility has a $1 billion exposure to Nord Stream 2, along with five power plants in Russia with a combined capacity of 11.2 gigawatts, providing about 5% of Russia's total energy needs.

Uniper and its controlling shareholder Fortum together own 12 power plants in Russia and employ 7,000 people there.

(Reporting by Reuters in Moscow; Editing by Emelia Sithole-Matarise)