Oil prices fell over 5% on Monday, deepening losses for the second straight day and hit a 2-week low due to fears over a global demand for fuel and increasing market surplus, due to the rapid spread of the Omicron variant in most parts of the world, and warnings from the World Health Organization.

US crude fell 5.2% to the lowest since December 6 at $66.67 a barrel, after opening at $70.35, and hit a high at $70.35, and Brent crude fell 4.6% to the lowest since December 3 at $69.64 a barrel, after opening at $72.76, and hit a high at $72.80.

The US crude lost 2.25% on Friday, and Brent fell 2.25%, due to the increasing Omicron cases.

Oil prices lost around 2.5% last week, the seventh straight weekly loss, due to renewed concerns about the market balance.

The spike in Omicron-Covid cases in Europe and the US raised concerns about the return of lockdown restrictions which would impact the global fuel demand.

The British Health Minister refused to rule out re-imposing further restrictions before the Christmas holidays, and British Prime Minister Boris Johnson is reportedly considering urging the public to limit household mixing at Christmas.

The Netherlands went into lockdown on Sunday, with more lockdown restrictions looming before the Christmas and New Year holidays in many European countries.

The World Health Organization said on Saturday that Omicron cases are doubling in 1.5 to 3 days in areas with community transmission, adding that there are still limited data on the clinical severity of Omicron.

Baker Hughes revealed on Friday that the US drilling and exploration rigs rose by 4 rigs to a total of 475, the highest level since the week ending April 10, 2020.

The increase in the US drilling activity boosted the US production by more than 47% since mid-2016 to a total of 13.1 million barrels per day in March 2020, and held recently around 11.7 million bpd due to the coronavirus pandemic, marking the US place as the world's largest oil producer.