Opponents of Russian President Vladimir Putin used an annual day of remembrance on Monday (October 30) for victims of Stalin's purges to say cases like the murder of reporter Anna Politkovskaya showed repression was creeping back. A gunman killed Politkovskaya -- a vocal opponent of Putin and critic of pro-Kremlin forces in Chechnya -- in her central Moscow apartment earlier this month. "Politkovskaya was an opponent of the state power; she was an opposition figure who criticising the authorities directly and openly, and challenging the criminal and political lawlessness. There are no other reasons for the murder of Politkovskaya but political ones. It's a very serious thing when the government allows the destruction of its opponents - this was not happening before," the head of the liberal opposition party Yabloko, Grigory Yavlinsky, said. Putin has called the murder of Politkovskaya a disgusting crime and urged the police to find her killers as quickly as possible. Hundreds of mainly older Russians laid flowers in the snow at a stone memorial outside the former KGB headquarters -- the Soviet Union's feared secret police -- to remember the millions who suffered during the Soviet Union. Some waved photos of Politkovskaya and carried banners criticising the Kremlin. Historians differ on the exact numbers, but agree Soviet officials sent millions of people to a vast network of prison camps -- known as the Gulag -- and excuted hundreds of thousands. "Society has not absorbed the tragedy of the past ... Today in Russia we see a revival of authoritarian methods of running the country," human rights group Memorial said in a statement. Putin, a former KGB spy who has called the Soviet Union's collapse a "geopolitical catastrophe", marked the day by telling government ministers they must not hide the crimes committed under Communist rule. "Our society must always know about it and remember it, so that no one never should have the slightest wish to repeat these elements of the past today or tomorrow," television stations showed Putin as saying.