Two Ukrainian soldiers have been killed in fresh fighting between government forces and pro-Russian rebels in the east even as a new truce takes effect, officials say.
Saturday's casualties came a day after the Ukrainian government and pro-Russian fighters agreed on a new truce that began from midnight at talks in the Belrussian capital Minsk.
The agreement is aimed at reinforcing a deal co-signed by France and Germany in February 2015 after a surge in violence in the industrial east of Ukraine.
The Organisation for Security and Cooperation in Europe (OSCE) had given warning that the bloodshed had reached levels not seen for months.
The deal came in advance of Orthodox Easter Sunday and covers holidays that include labour day on May 1 and the Soviet victory over Nazi Germany during World War II marked on May 9.
'No respect' for ceasefire
Lysenko said several attacks had been recorded after the new truce came into force.
"The enemy does not respect the ceasefire," he said.
"But we hope that it happened accidentally and the enemy will stick to the agreements that have been reached at the international level."
Leonid Kuchma, Ukrainian President Petro Poroshenko's envoy to the OSCE-mediated talks in Minsk, said multiple violations of the new agreement had been recorded in the villages of Shyrokyne, Avdiivka and Mariinka.
Speaking through Darka Olifer, his spokesperson, Poroshenko said Ukraine was sticking to the agreement and called on Russia and the rebels to respect the truce.
About 9,300 people have died and more than 21,000 have been injured since the revolt against Ukraine's pro-Western leadership erupted two years ago in the predominantly Russian-speaking east.
A series of truce agreements have helped reduce the violence, although sporadic clashes persist, preventing the two sides from reaching a political reconciliation deal.