Tensions have spilled over in the Ukrainian capital Kyiv over the issue of prisoners still held by pro-Russian separatists in the war-torn east, despite a ceasefire agreement which calls for their release.
Guards intervened to stop demonstrators demanding their freedom from reaching the presidential administration building.
Some of the protesters had wider concerns.
“We demand that the president listen to us. We demand an investigation and punishment for those who killed people during (last winter’s) Maidan protests. We demand that the army get proper supplies, not just promises,” said demonstrator Olexiy Batyuta.
Despite the ousting of the former government under ex-president Yanukovych, mistrust of the authorities remains high.
At one point the crowd turned angry, believing a provocateur was among them intent on causing trouble.
Some 1,340 Ukrainian prisoners have been freed under the ceasefire but the authorities say more than 600 are still being held by separatists.
The rebels claim they are seeking the release of around 400 from their side.
The ceasefire agreement – which has failed to stop the fighting – has been criticised as being too vague, and for lacking a mechanism for a prisoner exchange to take place.