PARIS, Jan. 7 (Xinhua) -- The International Energy Agency (IEA) said on Wednesday that it is unacceptable for Russia to turn off all gas supplies to Europe via Ukraine, urging both sides to reopen the pipelines as soon as possible.

    "Despite the reassuring statements late December by both parties that supply to Europe would not be interrupted, supplies have now come to a complete halt," the Paris-based agency said in a statement.

    The move is completely unacceptable, given that European customers are not a party in this dispute, it said, adding that the interruption is creating hardship for Europeans during the coldest weather the continent has faced in a number of years.

    The agency called on Russian company Gazprom and Naftogaz of Ukraine which are wrangling over their unpaid bill, to restart pumping immediately and work out a long-term agreement to settle their dispute.

    Tension between Russia and Ukraine has escalated since Tuesday.

    Ukraine was forced to cut off gas supplies to Europe, as Russiaon Wednesday completely stopped pumping to the country, said Valentyn Zemlyansky, spokesperson for Naftogaz.

    Ukraine sits on the main transit route for Russia's gas exports, with about 80 percent of Russian gas supplied to the EU passing through it.

    A similar dispute over gas prices between Kiev and Moscow erupted in 2006 when Gazprom cut all gas supplies to Ukraine, raising deep concerns among European customers.