MOSCOW/KIEV (AFP) - Russian state energy giant Gazprom on Wednesday halted all supplies of natural gas bound for Europe through Ukraine, equivalent to around a fifth of the European Union's total gas consumption. Gazprom said in a statement that it had been forced to act because Ukraine was preventing the transit of supplies as part of a bitter dispute between the two, which has disrupted gas deliveries across Europe. The company also said it was increasing supplies through Belarus and Turkey, as well as tapping underground gas reservoirs in Europe and buying gas on the spot market to try and make up for the shortfalls. "In unprecedented circumstances in which our European customers are not getting Russian gas anyway, we are forced to stop supplying it to Ukraine's gas system until Ukraine can offer guarantees for its full transit," Gazprom said. "Gazprom is taking all possible measures to fulfil its export commitments," the statement continued. Russian Prime Minister Vladimir Putin had ordered Gazprom to halt supplies through Ukraine earlier in the day. Russian news agencies reported that Gazprom's central control room in Moscow formally gave the order to stop all supplies to Ukraine after confirming that none of the gas intended for European consumers was crossing Ukraine. Meanwhile, the Ukrainian government and the European Commission on Wednesday agreed "immediately" to allow European Union technical observers into Ukraine to monitor gas supplies amid its dispute with Russia, the Ukrainian government said. The agreement came in telephone talks between Ukrainian Prime Minister Yulia Tymoshenko and European Commission chief Jose Manuel Barroso. "Yulia Tymoshenko and Jose Manuel Barroso have agreed to immediately send EU technical experts so that they conduct constant monitoring of natural gas supply volumes," the government said in a statement. Tymoshenko also told Barroso that Ukraine would "ensure ... uninterrupted transit" of gas once Russia resumes supplies to Europe through Ukrainian territory, the statement said. Tymoshenko also spoke by phone to German Chancellor Angela Merkel, who said Germany had supported sending the bloc's observers to Ukraine, a separate statement said. Germany, along with countries such as France, Germany, Italy and Serbia, reported drastic falls in Russian gas supplies. Meanwhile, Russian Prime Minister Vladimir Putin said Russia would resume gas supplies to Europe via Ukraine when a mechanism is agreed for deploying international observers. Putin made the comments in a telephone conversation with Czech Prime Minister Mirek Topolanek, whose country currently holds the European Union presidency, his press service said. "If Ukraine does not allow the transit of Russian gas (to Europe) in the nearest future and Russia is compelled to stop deliveries of gas in transit, then Gazprom will only resume deliveries when a control mechanism is worked out with the participation of international observers," Putin said. European Commission spokesman for energy issues Ferran Tarradellas had said earlier: "The commission is ready to consider sending observers to Ukraine if required and if the parties ask for it." He said that the idea would be for EU officials to "observe the volume of gas transiting between the two countries." The agreement on sending EU observers to Ukraine comes after a bitter dispute between Moscow and Kiev has seriously disrupted Russian gas deliveries to Europe in the depths of winter. The EU has so far been reluctant to take sides in the dispute. A member of an EU delegation that visited Kiev this week told AFP it did not want to take sides: "We are not here to mediate," he said on condition of anonymity Tuesday. "We are not here to do politics."