BP's Chief Executive Bob Dudley
BP's chief executive Bob DudleyReuters

BP chief Bob Dudley has reiterated that the oil giant will continue to work in Russia, despite tensions continuing to rise.

Speaking at the World Petroleum Congress in Moscow, Dudley said: "We continue to work and do business as usual."

BP holds an 18.5% stake in Russian oil giant Rosneft, whose CEO Igor Sechin will also attend the event.

The comments followed shortly after Gazprom's announcement that it would pursue payment from Ukraine's Naftogaz through Swedish courts and that it would not ship any further gas to the national utility without payment up front.

"From today the Ukrainian company will receive Russian gas only in the quantity that it has already paid for," Gazprom said in a statement.

Oil prices, meanwhile, have recently closed on a nine-month high, with the advancement of the Islamist group the Islamic State of Iraq and the Levant (Isis) placing question marks over Iraq's ability to continue to export oil.

Iraq is Opec's second-largest exporter after Saudi Arabia, with Opec member states responsible for one-third of the world's oil supply.

The conference in Moscow will host 5,000 delegates from the energy sector and will include an address from Russian president Vladimir Putin.

The week-long event takes place every three years, but rarely can it have taken place amid tensions as high as they currently are between the West and Russia.