MOSCOW, December 20./TASS/. The killing of the Russian ambassador to Turkey is particularly painful for Russia, the probe into this crime continues, Russian President Vladimir Putin said on Tuesday.

"Russian Ambassador Andrey Gennadievich Karlov was meanly killed in Istanbul yesterday. A thorough probe into all circumstances of this crime is underway," Putin said in his speech at a concert marking State Security Officers’ Day. "This (the murder) of course particularly painful for us," the president said.

Putin also said that Russia expresses sympathy for the Europeans over the latest terrorist attack in Berlin.

"We do know about what is happening in other countries, about the latest crime of this sort committed in Europe. Many people died in Berlin. We express sympathy and wish early recovery to those injured. We also address one and all with a fresh reminder that we have proposed many times and that we propose once again we should present a common front against international terrorism. This is the only way of attaining victory," Putin said.

Putin has ordered security services to step up cooperation with foreign colleagues to ensure security in Russia and in the world.

"I ask security services to take additional measures to ensure security inside Russia and outside it, to enhance the safety of Russian foreign missions and their staff," Putin said. "I ask you to step up work with secret services of other states through partner channels," Putin said.

The Russian leader instructed security services and the national anti-terror committee "to be maximally vigilant and mobilized."

As the Russian leader said, this referred to the Federal Security Service and other security agencies.

"And, of course, the coordinating role of the national anti-terror committee should remain at a high level. It is necessary to continue strictly and competently acting in all the anti-terror directions. They include neutralizing militants and their leaders, preventing terrorist crimes and cutting short the channels of terrorism financing," Putin said.

According to Putin, "serious attention should be paid to the struggle against extremism."

"It is necessary to resolutely cut short the propaganda of xenophobia and nationalism, including in social networks and prevent involving youths into radical groupings. Such an attempt is a real threat to the stability of our multinational society," Putin said.