Police in southern Russia have arrested three men from Central Asia for allegedly plotting a bomb attack, a week after Islamic State terrorists from Tajikistan killed 144 people at a rock concert in Moscow.

The three men “were plotting a terror attack with a bomb in a crowded place in the Stavropol region,” Russian news agency TASS, quoted a Federal Security Service (FSB) spokesman.

Russian security services did not specify which of the five former Soviet Central Asian countries the men were from. 

The FSB published a video of the men shopping for food and nails when its agents then swept in and wrestled them to the floor.

“Components of an IED, chemical substances and submunitions” were seized at the arrested men’s homes, according to Baza, a Telegram channel linked to Russia’s security forces.

Russia has been on edge since the attack on the Crocus City Hall venue in northwest Moscow, the worst terrorist attack in Russia in 20 years.

The attack was believed to be carried out by the Khorasan branch of the Islamic State, which operates out of Afghanistan and recruits people from Central Asia.

Since then, Central Asian governments have warned their citizens to expect a backlash.

There have been reports of attacks on a handful of Tajik businesses and cafes and the Russian police have stepped up their inspections of Central Asians’ documents.

Russian human rights group First Department also said that police were rounding up migrants and deporting them. It quoted an unnamed lawyer in St Petersburg saying that he had seen “at least two full planes” flying back to Central Asia.

“There are also raids on dormitories and apartments. All special detention centres are overcrowded,” the lawyer said.

Attackers fit a pattern 

Russian security forces regularly claim to break up Islamist terrorist cells. Earlier in March, the FSB killed two Kazakhs near Moscow. They were said to be plotting an attack on a synagogue.

Many migrant workers travel from Central Asia to work in Russia every year but they are often treated poorly and become vulnerable to Islamic State recruiters.

Edward Lemon, a Central Asia specialist and professor at Texas A&M University, said that the recruitment of the Crocus City Hall attackers appeared to fit this pattern.

“They migrated to Russia relatively recently, were not particularly religious and appear to have rapidly mobilised to violence,” he said.