Ukraine signed a deal Monday to allow independent monitors to track natural gas supplies from Russia to Europe, with no conditions, Russia's gas giant Gazprom said.

The agreement, which Gazprom said was signed Monday morning during talks in Kiev, could open the way for a resumption of gas shipments to Europe through pipelines that cross Ukraine.

The Ukrainian president's office and the prime minister's office both said they could not immediately confirm that the deal had been signed.

Russia has said the EU-brokered deal must be signed before it will restart supplies to other European countries. Russia stopped supplying gas to Ukraine on Jan. 1 amid a price dispute and on Wednesday stopped supplying countries beyond Ukraine because it claimed Kiev was siphoning off the gas. Ukraine has denied this.

Ukraine first signed the agreement early Sunday but then attached what it called a "declaration" with additional conditions. Russia said this voided the agreement.

Russia supplies about one-quarter of the European Union's natural gas, 80 percent of it shipped through Ukraine, and the disruption has come as the continent is gripped by subfreezing temperatures.

Sales of electric heaters have soared across eastern Europe, and thousands of businesses have been forced to cut production or even shut down.

The European Commission has strongly urged Russia to restore gas supplies, noting that monitoring teams had already reached gas facilities on Ukraine's eastern border. "There is no reason to further delay gas supplies," it said in a statement Sunday.

EU monitoring teams were also getting into place at other spots along Ukraine's vast pipeline system.

One team reached the Sudzha gas measuring station on the Russian side of the border with Ukraine on Sunday, while others were traveling to three gas pumping stations on Ukraine's border with EU countries.

EU monitors will also be in Kiev and Moscow, at the pumping centers for Ukraine's state gas company Naftogaz and Russia's state-run gas monopoly Gazprom.

Ukrainian officials said it would take three days for gas to reach Europe once Russia resumes supplies.