The foreign ministry added that “there are also casualties among Afghan citizens” without giving further details. “One of the embassy staff was an Afghan guard and we still don’t know the nationality of the second person,” a security source in Afghanistan told CNN. Another 10 people were injured in the explosion. Russia’s Investigative Committee said two employees killed were the embassy’s second secretary and a security guard. A Kabul police spokesman said the explosives went off in a crowd of people after an attacker was spotted and shot dead by Afghan security forces near the Russian embassy. “Today around 11 am local time a suicide bomber, who was planning to detonate his explosives among the crowd, was spotted and shot dead by security forces near the Russian Embassy in Kabul Police District 7. As a result, his explosives went off,” police spokesman Khalid Zadran said on Twitter. An ISIS member in Afghanistan claimed responsibility for the attack in a statement on Monday. CNN cannot independently verify the authenticity of this claim. Russian Foreign Minister Sergei Lavrov said additional Taliban forces had been brought in to secure the embassy in the Afghan capital. “Two of our comrades died. A number of measures were immediately taken to strengthen the protection of the outer perimeter,” Lavrov said during a meeting with Tajikistan’s foreign minister in Moscow. “Afghanistan’s intelligence and counterintelligence services are involved,” he added. Kremlin spokesman Dmitry Peskov described the attack as “unacceptable”. “This was a terrorist strike, it is absolutely unacceptable. We strongly condemn such terrorist acts. Of course, now the main thing is to get information about what happened to our diplomats. As far as I understand, the information will be updated.” Peskov said at a briefing on Monday. CNN’s Fred Pleitgen, Darya Tarasova and Hamdi Alkhshali contributed reporting.