An Islamic terrorist bomb plot to cause carnage on Moscow's Red Square was thwarted by a spam text message, a court heard today.

Ilyas Saidov was jailed for 15 years for organising the attack in which two women suicide bombers were supposed to wear explosive belts to be detonated by a mobile phone call.

But just hours before they were to strike on New Year's Eve 2010, one belt exploded after the detonator was activated by a spam text, killing one of the women and prompting the arrest of the other. She was sentenced to 10 years in jail in May.

Spam is a daily nuisance for many Russians buying new SIM cards but this time the message saved thousands from being in harm's way. Red Square is a popular gathering point for Muscovites to see in the new year.

Saidov, a member of an underground Islamist group, brought the belts from his native Dagestan, a southern province in the Caucasus region plagued by almost daily clashes between Islamists and federal forces.

The Moscow City Court also found Saidov guilty of gunning down two police officers and three civilians in Dagestan.

Saidov pleaded guilty and co-operated with investigators, giving up the leader and several members of an underground Islamist group he was part of. His testimony led to the killing of several Islamists.

Four members of the group have been convicted, and six more are currently standing trial, investigators said.

Since 2000, at least two dozen female suicide bombers, most of them from the Caucasus, have carried out terrorist attacks on security officers and civilians in Russian cities and aboard trains and planes.

The bombers are often called "black widows" in Russia because many of them are the wives, or other relatives, of militants killed by security forces.

Islamic militants are believed to convince "black widows" that a suicide bombing will reunite them with their dead relatives beyond the grave.