HANOI (Reuters) - Vietnam's maritime oil and gas operations are in accordance with international law and conducted in waters in which it has total sovereignty, the country's foreign ministry said in a statement on Thursday.

Rosneft Vietnam BV, a unit of Russian state oil firm Rosneft <ROSN.MM>, is concerned that its recent drilling in an area of the South China Sea that is claimed by China could upset Beijing, two sources with direct knowledge of the situation told Reuters on Wednesday.

"As we have repeatedly asserted, all of Vietnam's maritime economic activities, including oil and gas activities, have been licensed and carried out in maritime zones entirely under Vietnamese sovereignty and jurisdiction," foreign ministry spokeswoman Le Thi Thu Hang told Reuters in a statement.

Vietnam's oil and gas activities are conducted in accordance with the 1982 U.N. Convention on the Law of the Sea, Hang said.

(Reporting by Khanh Vu and James Pearson; Editing by Alexandra Hudson)