Oil prices extended gains for a third session on Monday, with Brent rising above $81 a barrel to its highest in more than four months, as wider U.S. sanctions are expected to affect Russian crude exports to top buyers China and India.

Russia's Foreign Ministry has denounced U.S. sanctions against Moscow's energy sector and said the country would carry on with large oil and gas projects.

The Biden administration has imposed some of its toughest sanctions yet on Russia, in a move designed to hit Moscow's energy revenue that is fuelling its war in Ukraine. The measures target more than 200 entities and individuals ranging from traders and officials to insurance companies, as well as hundreds of oil tankers.

Oil prices hit their highest level in more than three months on Monday's open, extending their rally on expectations that wider U.S. sanctions will affect Russian crude supplies to the world's top and third largest importers China and India.

India's oil import strategy is set for a major overhaul as the latest US sanctions on Russian producers and vessels threaten to disrupt supply lines. With nearly 36% of India's total oil imports coming from Russia last year,

The White House has announced new sanctions against Russian oil companies, which are expected to cost Russia billions of dollars per month. The restrictions target Gazprom Neft and Surgutneftegas, as well as 183 ships involved in oil exports.

By Nidhi Verma, Chen Aizhu, Siyi Liu and Florence Tan NEW DELHI/SINGAPORE (Reuters) - Chinese and Indian refiners will source more oil from the Middle East, Africa and the Americas, boosting prices and freight costs,