Rosneft has completed drilling at the Universitetskaya-1 well in the Arctic and discovered oil at the East-Prinovozemelskiy-1 licence area in the Kara Sea.
The company said the sea depth at the drilling site is 81m, while the designed depth of the vertical well is 2,113m.
The drilling resulted in obtaining samples of rock, drilling a pilot hole with an 8.5in diameter at a depth of 600m and collecting horizontal core samples.
Rosneft said it will analyse the data from the well and come to a conclusion on the reserves at the site.
Rosneft head Igor Sechin said: "The first oil was extracted. It is an astonishing sample of light oil, which, based on the results of the analysis performed, is comparable to the Siberian Light oil.
"The resource base estimate of just this oil trap is 338 [billion cubic metres] bcm of gas and more than 100 million tones of oil. And this is just the estimates of this very structure. This is an outstanding result of the first exploratory drilling on a completely new offshore field.
"This is our united victory; it was achieved thanks to our friends and partners from Exxon Mobil, Nord Atlantic Drilling, Schlumberger, Halliburton, Weatherford, Baker, Trendsetter, FMC."
The Universitetskaya structure covers a 1,200,000km area with a 550m-high hydrocarbon trap.
The site's resources amount to over 1.3 billion tonnes of oil equivalent and approximately 30 structures were identified in three East Prinovozemelskiy areas of the Kara Sea.
The entire resource base of the three areas is estimated at 87 billion barrels or 13 billion tonnes of oil equivalent.
According to experts, the amount of oil and gas in the Kara Sea oil province is comparable to the resource base of Saudi Arabia.