Polish president honours Katyn victims at Warsaw memorial

Polish President Andrzej Duda laid flowers on Friday at Warsaw's Tomb of the Unknown Soldier in tribute to more than 20,000 Polish prisoners of war executed by the NKVD Soviet secret police in Katyn, western Russia, and other locations in the spring of 1940.

"On April 3, 80 years ago, the Soviets started mass executions of Polish officers. Polish President Andrzej Duda paid tribute to the victims of the Katyn Crime at the Tomb of the Unknown Soldier," the President's Office wrote on Twitter.

The Katyn Forest Massacre in western Russia was a series of mass executions of Polish POWs, mainly military officers and policemen, carried out by the Soviet NKVD security agency in April and May 1940. The killings took place at several locations, but the massacre is named after the Katyn Forest in western Russia, where some of the mass graves of the victims were first discovered.

About 8,000 of the victims were officers imprisoned during the 1939 Soviet invasion of Poland, another 6,000 were police officers, the rest were Polish intellectuals, deemed by the Soviets to be intelligence agents and saboteurs.

In 1943, the government of Nazi Germany announced the discovery of mass graves in Katyn Forest. The Soviets claimed that the killings had been carried out by the Nazis in 1941 and denied responsibility for the massacres. In 1990, Russia officially acknowledged and condemned the perpetration of the massacre by the NKVD.