According to an official of the Sova Center, as reported in The Guardian, racist incidents are increasing at the horrifying rate of 30% every three months in Russia (hat tip to reader Jeremy Putley for pointing us to the article).

A blast that killed 10 people in a Moscow market on Monday was caused by homemade bombs planted by two students targeting Asian traders, officials said yesterday. Prosecutor Yuri Syomin said the pair carried out the attack because they thought there were "too many people [there] of Asian background, towards whom they experienced bad feelings".

The attack, which marks a sharp escalation in the campaign by Russian ultra-nationalists against immigrants, was originally thought to have been provoked by a business dispute.

However, Oleg Kostyryov and Ilya Tikhomirov, both 20-year-old university students, were charged with racially motivated murder. They were arrested at the scene of the explosion at the Cherkizovsky market in the north-east of the city, soon after it took place. A third man, Valery Zhukovtsov, is being questioned.

Russia has seen a rise in xenophobia in the past two years, expressed in a series of murders and beatings of people with dark skin, often from central Asia or the Caucasus. Markets have often been points of tension as immigrants work there, selling food, clothes and other goods.

Neither of the suspects is known to be a member of a neo-Nazi group, and their attack differed from a spate of recent racist killings in which the victims were stabbed, shot or beaten to death.

Mr Syomin said the two had confessed to the crime, and that components of makeshift bombs were found at the halls of residence where Mr Kostyryov lived. In a confused reference to Chechens, they told investigators their aim was to "get revenge on the 'illegals' who are filling up Russia and carrying out terrorist attacks".

According to police, the pair learned how to prepare a bomb on the internet. They used ammonium nitrate, aluminium powder, acetone and sulphuric acid, with an alarm clock detonator. Mr Kostyryov was a chemistry student at the Mendeleev Institute and may have used his knowledge to make the devices.

Police said earlier that Mr Kostyryov and Mr Tikhomirov had entered a building at Cherkizovsky at 10.30am on Monday and planted one explosive device each, concealed in a plastic bag. Surveillance pictures showed Zhukovtsov lagging behind them, without carrying anything.

The blast, which tore through shops and a walkway, killed 10 people and 40 had to be sent to hospital. Two of the dead were Russians but the others were citizens of Uzbekistan and Tajikistan.

Mr Kostyryov and Mr Tikhomirov are thought to have planned the attack weeks in advance and recruited Zhukovtsov last weekend to help them escape afterwards.

Kamilzhan Kalandarov, a Muslim leader and member of the government-controlled Public Chamber (an ombudsman body), said the attack showed xenophobia had reached a dangerous level, with nationalists opting for the use of terror.

The blast was "not an instance of banditry, but a large-scale mass terror attack motivated by ethnic enmity," he told Interfax.

Galina Kozhevnikova of the racist violence monitor Sova said: "This demonstrates the quick growth of ultra-right tendencies. We are seeing a 30% increase in xenophobic attacks every three months."