Oil prices slumped more than 3% on Dec. 20 as surging cases of the Omicron coronavirus variant in Europe and the U.S. stoked investor worries that new mobility restrictions to combat its spread could hit fuel demand.

Brent crude futures fell $2.42, or 3.2%, to $71.10/bbl by 1005 GMT while WTI crude futures in the U.S. were down $2.79, or 3.9%, at $68.07.

“Simply put, it is not a case of if but when governments impose tougher restrictions,” said Stephen Brennock of broker PVM in a report.

“Both crude markers are taking a sharp dive as the new week gets underway amid the prospect of a bigger than expected Omicron-spurred dent to global demand.”

The Netherlands went into lockdown on Dec. 19 and the possibility of more COVID-19 restrictions being imposed ahead of the Christmas and New Year holidays loomed over several European countries.

U.S. health officials urged Americans on Dec. 19 to get booster shots, wear masks and be careful if they travel over the winter holidays, as the Omicron variant raged across the world and was set to take over as the dominant strain in the United States.

Meanwhile, U.S. energy firms this week added oil and natural gas rigs for a second week in a row.

The oil and gas rig count, an early indicator of future output, rose by three to 579 in the week to Dec. 17, its highest since April 2020, energy services firm Baker Hughes Co. said in its closely followed report on Dec. 17.

Still, lower exports are expected from Russia with exports and transit of oil from the country planned at 56.05 million tonnes in the first quarter of 2022 versus 58.3 million tonnes in the fourth quarter of 2021, a quarterly export schedule seen by Reuters showed on Dec. 17.

Meanwhile OPEC+ compliance with oil production cuts stood at 117% in November, up a percent from the previous month, two sources from the group told Reuters, as output continues to lag agreed targets.