Exxon Mobil Corp. signed a deal with Russia's Rosneft on Thursday to develop oil and gas resources in the Black Sea, the Associated Press has reported.

Exxon Mobil Chairman and CEO Rex Tillerson announced the deal with Rosneft Chairman and Russian Deputy Prime Minister Igor Sechin at the World Economic Forum in Davos, Switzerland. The deal represents a new boost to the country's lucrative energy sector despite concerns about the challenges of investing there.

Exxon Mobil Chairman Rex Tillerson (L) listens on Thursday to Russian Deputy Prime Minister Igor Sechin during a press conference at the World Economic Forum in Davos, Switzerland.

"It's an important opportunity to expand our activities to new areas now," Tillerson told reporters during the announcement. Sechin hailed the deal as a sign that Russia is open for investment.

The deal is Exxon Mobil’s second recent attempt to do business in the Black Sea.

The Deepwater Champion, a drill ship contracted by Exxon, set sail Sunday to explore oil along the Black Sea shores of Turkey in a joint exploration project with the Turkish Petroleum Corporation, or TPAO.

Exxon Mobil committed to drill two wells in the Black Sea, TPAO Director Mehmet Uysal told Anatolia news agency in a recent interview.

“In case oil is found, TPAO will join the investment. Exxon Mobil will get retrieve expenses from the oil recovered,” Uysal said.

Oil giant BP announced a deal with Rosneft on Jan. 14 to exploit the Arctic Sea and BP chief Bob Dudley insisted that he was confident about the investment climate in Russia, despite his company’s previous difficulties with Russian investments, AP reported.

Exxon Mobil was on the verge of buying a large share of Russian company Yukos before its chief, Mikhail Khodorkovsky, was jailed in 2003, in a case that has stained Russia's investment reputation for the past eight years.

Khodorkovsky has accused Sechin of initiating the legal onslaught against him and Yukos, once Russia's largest and fastest growing oil company. Yukos' prime assets were passed to Rosneft – now Russia's largest oil company.

Concerns about Russian legal problems, state interference and security – especially following a deadly airport bombing in Moscow on Monday – have surfaced at the Davos forum.

Russian President Dmitry Medvedev gave a speech Wednesday night in which he insisted that investors should not be scared away.