Political tensions were fueled in part by allegedly Chechen or pro-Chechen terrorist and criminal activity in Russia, as well as by border clashes. On 16 November 1996, in Kaspiysk (Dagestan), a bomb destroyed an apartment building housing Russian border guards, killing 68 people. The cause of the blast was never determined, but many in Russia blamed Chechen separatists. Three people died on 23 April 1997, when a bomb exploded in the Russian railway station of Armavir (Krasnodar Krai), and two on 28 May 1997, when another bomb exploded in the Russian railway station of Pyatigorsk (Stavropol Krai). On 22 December 1997, forces of Dagestani militants and Chechnya-based Arab warlord Ibn al-Khattab raided the base of the 136th Motor Rifle Brigade of the Russian Army in Buynaksk, Dagestan, inflicting severe losses on the men and equipment of the unit.