 Complete the following phrase:  On 3 April 2017, a terrorist attack using an explosive device took place on the Saint Petersburg Metro between Sennaya Ploshchad and Tekhnologichesky Institut stations. Seven people including the perpetrator were initially reported to have died, and eight more died later from their injuries, bringing the total to 15. At least 45 others were injured in the incident. The explosive device was contained in a briefcase. A second explosive device was found and defused at Ploshchad Vosstaniya metro station. The suspected perpetrator was named as Akbarzhon Jalilov, a Russian citizen who was an ethnic Uzbek born in Kyrgyzstan. Prior to the attack, Chechen separatists had been responsible for several terrorist attacks in Russia. In 2016, ISIS had plotted to target St. Petersburg due to Russias military involvement in Syria, resulting in arrests. No public transport system in Russia had been bombed since the 