The head of Russia's police force said the number of terrorist attacks in the country had halved since 2011, though he gave no actual figures on the issue, long shrouded in murky statistics.

"We're observing a downward trend in terror crimes during the past three years. The number of terror attacks has decreased by half," Interior Minister Vladimir Kolokoltsev said, according to RIA Novosti.

Kolokoltsev, who spoke before the Federation Council, also complained that news outlets were making "heroes" out of terrorists by reporting about their lives. That statement comes hot on the heels of a high-profile suicide bombing that killed six in the southern city of Volgograd.

The attack was blamed on the North Caucasus' Islamist insurgency, a leader of which recently lifted a moratorium on attacks on Russian civilians. That move raised questions about security at the upcoming Winter Olympics, to take place in the Caucasus Mountains.

No common federal statistics are available for terrorism-related crimes in Russia.

The Interior Ministry has said there were 622 "terror-related crimes" in 2011, including 29 actual terrorist attacks. The Federal Security Service reported 365 such crimes for the same year. Then-President Dmitry Medvedev put the figure at 94, and the Sydney-based Institute for Economics and Peace has said there were 184.