Ukraine's President Viktor Yanukovich is set to return to work on Monday after a period of sick leave, a statement on the presidential website said. Thousands of anti-government protesters have gathered in central Kiev to demand his resignation.
Ukraine's energy minister says protesters have been prevented from trying to seize the main energy ministry building in Kiev.
"About 100 people came, armed. I went to them and said that if they did not peacefully leave the building then the whole energy system of Ukraine could collapse," he said.
He said protesters left the building but he had been told they were blocking entry to the building outside.
He described the incident as a "direct threat to the whole Ukrainian energy system".
Ukraine has experienced difficult days before but few have been so complex or so pivotal.
The Ukrainian government says it is is ready to use all tools available to restore order if violence and unrest continues.
These are difficult days for Ukraine, a country edging toward its second revolution in a decade.