Moscow's Gazprom could cut Moldova's gas supply if the country does not settle its bill and sign a new contract, the energy giant's top official was quoted by Russia's Interfax news agency as saying.
Moldova declared a 30-day state of emergency on Friday in an effort to secure the ex-Soviet country cheaper natural gas from Europe after Moscow - its traditional supplier - raised prices.
Gazprom's Sergei Kupriyanov said Chisinau owed the company $709 million (610 million euros).
Moldova's contract with Gazprom ran out in September, but Kupriyanov said the pair were able to "meet half way" and extend a contract for October.
"If payment for gas supplies is not fully paid and a contract is not signed from December, then Gazprom will halt gas supplies to Moldova," he told Interfax.
The country of 2.6 million people wedged between Romania and Ukraine gets gas from Russia via its pro-Russian separatist region of Transnistria and Ukraine.
Gazprom this month hiked prices more than 40 percent to $790 per thousand cubic metres from $550 - a level Deputy Prime Minister Andrei Spinu said was "not justified and not realistic" for Europe's poorest country.
Despite the contract being extended, Moldovan Prime Minster Natalia Gavrilita said on Friday the country was receiving a third less natural gas than usual for October.
"We face a critical situation," she said.
She told parliament Moldova would be seeking supplies from EU countries and thanked Romania and Ukraine for already providing some gas.
The month-long state of emergency, which will last until November 20, gives Moldovan utility company Energocom the powers to secure gas from other countries.
The country's gas shortages come amid skyrocketing gas prices that some in Europe have blamed on Moscow not providing additional supplies to put pressure on the continent.