Gas disruption by Hungary to Ukraine breaks European solidarity and worries European officials.

Hungary's decision to cut the flow of natural gas to Ukraine is worrisome and has broken European solidarity on the issue, a top European official said Wednesday.

Due to the crisis between Ukraine and Russia over the price of gas, Ukraine is currently without direct supplies from Russia, its major source of gas. Thus, Ukraine began supplying its natural gas through reverse flow from Hungary.

But last week, Hungary cut its flow of gas to Ukraine, claiming it was due to a technical problem.

However, an official with a group that coordinates European energy policy was critical of the move.

"The principle of solidarity, the cornerstone of the Energy Community, would have required a coordination with the Ukrainian side at least," Dirk Buschle, Energy Community Deputy Director, told Anadolu Agency. "The situation in Ukraine is critical, and we have to work jointly to help them coming through the winter."

The Energy Community, a group established between the EU and a number of other countries, seeks to import EU energy policy into non-EU countries. The Energy Community Treaty, signed in 2005, binds the parties -- EU members and a number neighboring countries -- to implement a harmonious policy towards common problems. Ukraine signed the treaty in 2011.

Hungary joined the EU in 2004 and is therefore also a party to the treaty.

Hungary has sent 6.1 billion cubic meters of gas per year -- 16.8 million per day -- to Ukraine since March 2013. The decision to cut the gas flow to Ukraine seems to create a serious threat for Kiev just before the winter.

The Energy Community has sent a questionnaire to the Hungarian gas transmission system operator to find out if there is a contractual justification for this disruption, but has not yet received a reply, said Buschle.

"The community is very worried about the latest disruption of gas flows from Hungary to Ukraine. Both countries are part of an internal market for gas, the Energy Community. Under our treaty, maintaining the free flow for gas is mandatory also for Hungary," Buschle said.

A commercial precaution

"Hungary was affected by previous supply crises and it is reasonable to exercise a degree of caution, for example by filling up its underground storage facilities," said Anastasios Giamouridis, a senior consultant at Poyry Management Consulting Ltd., based in UK.

Hungarian stores are currently 63 percent full and contain approximately 3.9 billion cubic meters of gas, which is one of the lowest capacities in Europe and poses an unfavorable situation for Hungary compared to its neighboring countries, Giamouridis said.

He said that the current storage is still lower compared to the 76 percent -- roughly 4.7 bcm-- which Hungary had injected to its storages by the end of September, 2010, in the aftermath of the last serious supply cuts to Europe due to a Russia-Ukraine dispute.

Hungary consumed 9.6 bcm of gas last year.

FGSZ, Hungary's state-run gas pipeline network operator said Thursday they had halted the gas flow to Ukraine because of technical problems.