MOSCOW, Dec 20 (Reuters) - The Russian rouble fell to a near two-week low on Monday, under pressure from falling oil prices, global concerns over the Omicron coronavirus variant and simmering East-West tensions over Ukraine. At 0753 GMT, the rouble was 0.1% weaker against the dollar at 74.23 , after earlier touching 74.50 for the first time since Dec. 7. It had lost 0.3% to trade at 83.57 versus the euro . Brent crude oil , a global benchmark for Russia"s main export, was down 2.8% at $71.46 a barrel. Lower oil prices and the active spread of Omicron created a negative external backdrop for the rouble, said Promsvyazbank analysts, warning that the unit could weaken towards the 75 mark versus the dollar. The possibility of fresh COVID-19 restrictions being imposed ahead of the Christmas and New Year holidays loomed over several European countries, limiting risk appetite. read more "On the "Ukraine" front, the angst-ridden status quo simmers," said BCS Global Markets in a note. The West is concerned about Russia"s military build-up near its border with Ukraine, while Moscow has dismissed such concerns saying it has the right to move its troops within Russian territory as it deems necessary. Germany on Sunday said NATO would discuss Russia"s security proposals but would not let Moscow dictate the alliance"s military posture. read more The rouble did gain some short-lived support on Friday as the central bank hiked its key rate by 100 basis points to 8.5%, a move priced in by the market, and said more than one rate increase was still possible in the coming months. read more Russian stock indexes fell. The dollar-denominated RTS index (.IRTS) was down 1.9% at 1,552.6 points. The rouble-based MOEX Russian index (.IMOEX) was 1.8% lower at 3,657.8 points. For Russian equities guide see For Russian treasury bonds see