https://en.wikipedia.org/wiki/1999_Russian_apartment_bombings
In September 1999, a series of explosions hit four apartment blocks in the Russian cities of Buynaksk, Moscow, and Volgodonsk, killing more than 300, injuring more than 1,000, and spreading a wave of fear across the country. The bombings, together with the 1999 war of Dagestan, triggered the Second Chechen War.[1][2] The handling of the crisis by Vladimir Putin, who was prime minister at the time, boosted his popularity greatly and helped him attain the presidency within a few months.
Four apartment bombings took place and at least three attempted bombings were prevented.[26] All bombings had the same "signature", based on the nature and the volume of the destruction. In each case a powerful explosive was used, and the timers were set to go off at night and inflict the maximum number of civilian casualties.[27][28] The explosives were placed to destroy the weakest, most critical elements of the buildings and force them to "collapse like a house of cards".[29] The individuals behind the bombings were able to obtain or manufacture several tons of powerful explosives and deliver them to numerous destinations across Russia.
Although the bombings were widely blamed on Chechen terrorists, their guilt was never conclusively proven.[14] A number of historians and investigative journalists have instead called the bombings a false flag attack perpetrated by Russian state security services to win public support for a new war in Chechnya and to boost the popularity of Vladimir Putin prior to the upcoming presidential elections. Former FSB agent Alexander Litvinenko, who blamed the FSB for the bombings and was a critic of Putin, was assassinated in London in 2006. A British inquiry later determined that Litvinenko's murder was "probably" carried out with the approval of Vladimir Putin and Nikolai Patrushev.