(CNN) Two Russian embassy employees were among six people killed in a suicide blast near Russia's embassy in Kabul on Monday.
Russia's foreign ministry said in a statement that "an unknown militant set off an explosive device. As a result of the attack, two employees of the diplomatic mission were killed."
The foreign ministry added that "there are also victims among Afghan citizens" without giving further details.
"One of the employees of the embassy was an Afghan guard and we still do not know the nationality of the second person," an Afghan security source told CNN. Another 10 people were injured in the blast. Russia's Investigative Committee said that two staff killed were the embassy's second secretary and a security guard.
Kabul's police spokesman said that explosives went off in a crowd of people after an attacker was identified and shot by Afghan security forces near the Russian embassy.
"Today around 11 a.m. local time a suicide bomber, who was planning to blow up his explosives among the crowd of people, was identified and shot by the security forces near the Russian embassy in Police District 7, Kabul. As a result, his explosives went off," police spokesman Khalid Zadran said on Twitter.
An ISIS affiliate in Afghanistan claimed credit for the attack in a statement on Monday.
CNN cannot independently verify the authenticity of this claim.
Russian Foreign Minister Sergey Lavrov said additional Taliban forces had been brought in to secure the embassy in the Afghan capital.
"Two of our comrades have died. A set 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. The "intelligence and counterintelligence services of Afghanistan are involved," he added.
Kremlin spokesman Dmitry Peskov described the attack as "unacceptable."
"This was a terrorist attack, they are 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 told a briefing Monday.