The country's foreign ministry has told citizens to avoid unnecessary travel to Russia after last week's deadly shooting.
More than 130 people were killed in the terror attack on the Crocus Concert Hall near Moscow.
The attack has increased existing anti-immigrant sentiment in Russia, especially towards migrant labourers from the predominantly Muslim countries of Central Asia.
The four suspects are from Tajikistan and are in pre-trial detention.
Islamic State has said it was responsible for the attack and released footage of the massacre.
Hundreds of thousands of people from Tajikistan, Uzbekistan, and Kyrgyzstan work in Russia, and some have already said it has become tougher for them to do so.
https://news.sky.com/story/ukraine-russia-war-news-putin-zelenskyy-latest-live-updates-12541713
