The Security Service operatives and police have made arrests in connection with a bombing in Kharkiv, Ukraine, on February 22 that claimed four lives, Ukraine's National Security and Defense Council said.

"In a special operation in Kharkiv today, another five members of the terrorist group were detained," the council said in a statement on Thursday, citing its secretary, Oleksander Turchynov."

"They had weapons and ammunition, including plastid, detonators for explosives and hand grenades, seized from them," Turchynov said as quoted in the statement. The detainees included "the organizer of the crime and direct executors of the terrorist act," he added.

"Another two criminals connected with this group have been detained by [police] in Mariupol, where they were preparing a terrorist act. Ten kilograms of TNT was seized over the course of their detention," he said.

The attack was carried out outside the Sports Palace when a column was being formed for a procession to mark the first anniversary of the Revolution of Dignity. Two people were killed on the spot and another two were injured and died in the hospital.