Russian state-controlled oil giant Rosneft's shares jumped to an eight-month high in Wednesday afternoon trading as the markets reacted to news it was taking over TNK-BP, according to Moscow Exchange data.

As of 12:00 p.m., Rosneft’s stock climbed by 2.3 percent to 231 rubles ($7.70) per share, the highest level since early February, while the MICEX stock index was down 0.4 percent.

Investors were cheered by the deals struck by Rosneft with British oil giant BP and the AAR consortium of Russian billionaire shareholders, to repurchase their 50-50 stakes in TNK-BP, Russia’s third-largest oil producer. Rosneft and BP announced their deal on Monday, following a BP board meeting on Friday. Rosneft said last week it had made a provisional agreement to buy AAR's stake.

The deals will allow Rosneft to boost crude output to 200 million metric tons of oil annually and capture 5 percent of the global oil output, Rosneft CEO Igor Sechin said on Tuesday.

“Oil production will rise from 2.4 million barrels per day to 4.1 million bpd and overall output (of hydrocarbons) will grow to 4.6 million barrels (of oil equivalent) per day from the current 2.6 million bpd,” Sechin said in a conference call with investors.

Investors also responded positively after Russian Economics Minister Andrei Belousov said on Wednesday on the sidelines of Sberbank's business breakfast with members of the Valdai discussion club that the increase of BP’s stake in Rosneft as a result of its deal would not alter the prospects for Rosneft’s further privatization.

BP will acquire a total 18.5 percent stake in Rosneft in addition to the 1.25 percent it already held in the Russian company. It will also get two seats on Rosneft's nine-seat board.

“Rosneft is one of the companies where the readiness for privatization is the highest,” he said.

Under Russia’s plans for privatization of large state assets, the government is scheduled to withdraw from Rosneft’s capital by 2016.

Meanwhile, Moody's Investors Service has placed the ratings of oil giant Rosneft and TNK-BP on review for downgrade following Rosneft's announcement it intends to acquire 100 percent of the Russian-British joint venture, Moody's said on Wednesday.

“While the transaction has many positive attributes for Rosneft from a strategic and operational perspective, Moody's decision to place the ratings of both companies on review for downgrade reflects the considerable scale of the proposed transactions,” Moody’s said in a statement.

“Overall, the transactions may involve Rosneft paying approximately $45 billion, including through existing cash balances and new debt,” the rating agency said, adding further action would depend on the structure of the transaction's financing and its impact on financial metrics.