EU diplomacy chief Josep Borrell on Tuesday attended a course for Ukrainian law enforcement personnel near Kyiv, carried out by gendarmes from several EU countries, including France and Spain.
The course focused on the challenges security forces face in territories recently returned to Ukrainian control.
"(Officers) face difficult situations when they retake control of the liberated territories... they have to restore law and order," Borrell said.
The visit featured an exercise where participants had to carry out the risky -- but simulated -- arrest of dangerous residents.
"This kind of thing happens in reality," said Borrell, as the head of the mission, Portuguese National Guard officer Helder Carcao, showed him around.
The mission involves 10 officers from France, Spain, Portugal and Lithuania.
"We are training more than 150 members of the national police and the national guard who will become trainers" themselves, Borrell said.
Borrell added that the operation aimed to "provide training to thousands of security officers."
The course also prepares officers to deal with the discovery of war crimes and mass graves.
"Discovering mass graves and then having to inform the relatives, this is not a joke, this is something that has to be done with adequate psychological capacities," Borrell said.