Ukraine's acting President Oleksandr Turchynov told the country's parliament Tuesday that an "anti-terrorist operation" is under way in part of Ukraine's eastern Donetsk region.
"It will be conducted step by step, responsibly, carefully," he said, according to the Ukrinform news agency.
The reported operation comes as EU defense ministers and NATO chief Anders Fogh Rasmussen meet in Luxembourg with the crisis in Ukraine high on the agenda.
Turchynov had given pro-Russian protesters in other eastern Ukrainian cities until 2 a.m. ET Monday to disarm or face a "full-scale anti-terrorist operation" by Ukraine's armed forces.
But the deadline passed with no sign that it was heeded, including in the eastern city of Donetsk, where protesters have held the regional government building for more than a week. Similar deadlines in the past have come and gone with no consequences.
A U.N. human rights report released Tuesday on the situation in Ukraine, including the Crimea region annexed by Russia last month, cited an urgent need to counter "misinformation, propaganda and incitement to hatred" in the country to avoid the further escalation of tension.
"Facts on the ground need to be established to help reduce the risk of radically different narratives being exploited for political ends," said U.N. High Commissioner for Human Rights Navi Pillay.
Based on information gathered by U.N. human rights monitors since March 15, the report draws concerning parallels between what happened in Crimea and events unfolding in eastern Ukraine now.