First confirmation by investigators of bomber's origin;
Identity of 20-year old male known, but not released;
Investigators believe foreigners targeted

MOSCOW - The suicide bomber who killed at least 35 people at Moscow's main airport on Monday was a 20-year-old native of the North Caucasus, Russian investigators said, noting the blast location showed foreigners were targeted.

Federal Investigative Committee Spokesman Vladimir Markin's announcement on Saturday was the first official confirmation the bomber came from Russia's volatile North Caucasus.

"We will not release his name today...because the investigation to identify and apprehend the organisers and accomplices is still ongoing," he told reporters in a televised address.

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No group has claimed responsibility for the attack at the Domodedovo airport that killed at least eight foreigners. It bore the hallmarks of Caucasus insurgents.

Russia's leaders are struggling to contain a growing Islamist insurgency in the region, a strip of impoverished, mainly Muslim provinces along predominantly Orthodox Christian Russia's southern border.

The head of the mainly Muslim North Caucasus province of Ingushetia on Thursday also said the bomber stemmed from the region.

"These leaders of the North Caucasus underground are responsible, like Doku Umarov," Yunus-Bek Yevkurov told reporters in Ingushetia's capital, Magas, referring to a Chechen rebel chief who calls himself emir of the "Caucasus Emirate".

"The Caucasus Emirate did it, I am sure they did it," he told journalists at his heavily-guarded palace.

Press reports have also focused on a separate group from neighboring Dagestan, the Nogai Jamaat.

The bombing in Domodedovo's arrivals hall also suggested that militants were attempting to hinder government efforts to attract foreign investors.

The attack came days before President Dmitry Medvedev flew to the Davos forum to urge business leaders to increase investment in his country.