The second blast took place at the Park Kultury station near the Gorky Park in the third carriage of the train heading for the city centre, killing at least 12 people and injuring another 12 passengers, Emergency situations ministry spokesperson Irina Adrianova told state-run Rossiya 24 news channel.

The blasts were carried out by female suicide bombers, according to preliminary investigation by the FSB press office.

The bodies of the suicide bombers have been recovered from the blast sites on both the stations.

Meanwhile, the police have cordoned off the roads near the Lubyanka square and Park Kultury station and ambulance helicopters are landing there to evacuate the injured.

The Moscow prosecutor has confirmed the death of 37 people, while the number of injured on the Park Kultury station has risen to 20 and more people are being evacuated.

The spokesperson of the Prosecutor's Investigation Committee Vladimir Markin said the case of terror attacks have been opened in the two blasts.

Meanwhile, a column of black smoke was seen rising from the Park Kultury metro station and traffic chaos resulted at the nearby Garden Ring Road.

The rescuers have pressed helicopters into service to evacuate the injured to hospitals. Special buses have been pressed in to take stranded passengers to their destination.

The Red Line, Moscow's oldest metro line traverses the Russian capital from north-east to south-west and has transfer links with all the city underground lines.

On weekdays at least one million commuters use this line on which several railway stations are also located.

The blasts in the underground railway stations have revived the nightmare Moscow had witnessed on February 6, 2004 when a suicide bomb blast on a moving metro train had claimed 42 lives.

Same year in August in a botched attack 10 people were killed outside another metro station. Since then the perpetrators and organisers linked to Chechen terrorists were apprehended and sentenced.

The local media says the possibility that the fresh attack could be a revenge for the killing of two prominent warlords in security operations in Chechnya, including an Arab and a Russian converted to Islam, cannot be ruled out.