The shutoff came as Ukraine's newly elected President Viktor Yanukovych traveled to Brussels on his first official foreign visit to discuss energy security and other issues with EU leaders.

Ukraine's Fuel and Energy Ministry spokesman Fent Di said the shutoff, which could end by April 1, occurred because no Ukrainian firms put in bids to sell the electricity due to a coal shortage in Ukraine.

“It was no longer profitable for the firms to carry out the exports,” Di said.

The amounts represent a small share of the countries' electricity markets, and the shutoff did not appear to have much of an impact. The Hungarian Energy Ministry and the Romanian Economy Ministry could not immediately confirm that a shutoff had taken place, and a Slovak Economy Ministry spokesman said he did not know that Ukraine exported power to Slovakia.

Still, the incident could work against Yanukovych as he tries to assure Europe that Ukraine is a reliable energy partner.

The companies that account for about half of the export volumes are controlled by the government of Prime Minister Yulia Tymoshenko, who lost to Yanukovych in last month's presidential vote and has remained a fierce critic of him.

Asked when exports could resume, Larysa Kaznokh, a representative of government-controlled power exporter Zakhidenergo, said politics could play a role in resolving the situation.

“We will see how the situation will go in the government, how the new president and his team will react,” she said.

Mikhail Pogrebinsky, a political analyst in Kiev, said disruptions in trade like this could be linked to the power struggle that has ensued since Yanukovych pledged to oust Tymoshenko after taking office.

“It's possible that while we wait for the government's ouster, the tone of trade transactions, including partners, could change,” Pogrebinsky said.

But energy analysts said the incident is most likely a coincidence.

“I think exports will be renewed. There are no signs of trouble that energy exports have been undermined,” said Volodymyr Saprykin of the Razumkov Center.