By Guy Faulconbridge
MOSCOW (Reuters) -Russian President Vladimir Putin on Tuesday called for a new approach to migration after Tajiks living in Russia were detained for a deadly attack on a concert hall outside Moscow that killed at least 144 people and wounded 551 more.
Islamic State, the militant group that once sought control over swathes of Iraq and Syria, claimed responsibility for the mass shooting. Russia has said it suspects Ukraine was linked to the attack, a claim denied by Kyiv and dismissed by Washington.
At least 12 people - including four accused gunmen - have been detained in Russia in connection with the attack. Most are Tajiks who had lived and worked in Russia.
Putin told police chiefs that the attack was aimed at sowing discord, xenophobia and Islamophobia inside Russia. But he said that migration systems needed improvement, as it was clear that work permits were sometimes being issued to people with serious criminal records.
"We need to deeply and radically update our approaches to migration policy," Putin said, adding that some people with almost no knowledge of Russian or Russian culture were being allowed to work without proper checks.
"The decisive principle should be that only those who respect our traditions, language, culture, and history can come to live and work in Russia."
Russia's room for manoeuvre on migration, though, is limited.
Millions of people from former Soviet republics in Central Asia have flocked to Russia's biggest cities over the past few decades, supporting a blossoming 24-hour consumer society by working as taxi drivers, cleaners, barbers or beauticians.
With Russia's 147 million population forecast to fall over future decades, migrants play an vital role in the economy, also working in heavy industry and farming.
"It is necessary to ensure the interests and security of the state and society, to conserve and preserve interethnic and interreligious harmony, our cultural and linguistic identity, all that is Russia's strength," Putin said.
At least 277 languages and dialects are spoken in Russia. About 10% to 15% of Russia's population are Muslims.
Tajik officials have said they have seen a rise in Tajiks leaving Russia since the attack, and Russian media have reported police raids against unregistered migrants.
A blast ripped through a Central Asian-themed cafe in the southern Russian city of Voronezh in the early hours of Monday, when no one was on the premises.