A group of suspected suicide bombers was detained in Russia's North Caucasus republic of Dagestan, the National Antiterrorism Committee (NAC) said on Monday.

The NAC press center said six women aged between 15 and 29, and two men (ages unspecified) were detained in the Dagestan capital of Makhachkala following a tip-off that an underground organization was plotting a series of terrorist attacks in central Russia.

It added that "farewell letters" were discovered on the suspects.

The NAC also said that four of the female detainees were the widows of former militant leaders, and the other two had previously been convicted of illegally storing weapons and were listed as missing.

The detainees are being questioned while special services search for their handlers.

According to the NAC, one of the detained men is suspected of assisting in smuggling to Moscow the suicide bombers responsible for the metro blasts in the capital on March 29, which killed 40 people.

MOSCOW, July 12 (RIA Novosti)