The Imam Shamil Battalion said the attack in the Russian city was carried out on the orders of al-Qaeda leader Ayman al-Zawahiri.
Its statement has been circulated by high-profile al-Qaeda supporters on the Telegram messaging app.
The attack in St Petersburg killed 16 people, including the suicide bomber.
Russian officials later said Akbarzhon Jalilov, a Russian citizen born in Kyrgyzstan, detonated a bomb between two metro stations in the city.
The Imam Shamil Battalion statement said the bombing was revenge for Russian military actions in Muslim countries such as Syria and Libya as well as the Muslim region of Chechnya in Russia's North Caucasus.
More attacks were being planned, the statement said.
The authenticity of the claim has not been independently verified.
It emerged in news outlets used by jihadists in Africa, including the Mauritania-based website Agence Nouakchott Info, but has not appeared on official al-Qaeda channels.
The Russian authorities have so far made no comment.
Analysts say the name of the group claiming the bombing may be a reference to Imam Shamil - a 19th Century leader of anti-Russian resistance in the Caucasus.
Ten people have been detained in Russia in connection with the bombing.
Last week, Abror Azimov, one of the suspects, denied he was behind the attack. Mr Azimov, who is reported to be from Kyrgyzstan, said he simply "followed" instructions and "did not realise" what he was doing.
It came shortly after his lawyer told Russian media he had "fully confessed" to being behind the blasts.
|The blast took place between two metro stations in St Petersburg. AFP|
Group with alleged al-Qaeda ties claims St. Petersburg metro bombing
A group called the Imam Shamil Battalion has claimed responsibility for the deadly bombing on the St. Petersburg metro, a US monitor has said. The statement also said the bomber was acting on orders from al-Qaeda.
More than three weeks after a bomb blast killed 15 people on a metro train in the Russian city of St. Petersburg, a group has claimed responsibility for the attack, a monitoring group said Tuesday.
According to the SITE Intelligence Group, a little-known organization called the Imam Shamil Battalion said it had carried out the attack. The group also said the bomber acted on instructions from al-Qaeda leader Ayman al-Zawahiri.
The claim was originally published by the Mauritanian news agency ANI, which is often used by West and North African jihadist groups to release statements.
The attack on April 3 tore through an underground train traveling between metro stations in Russia's second-largest city, killing 15 and wounding around two dozen. The alleged suicide bomber, Akbarjon Djalilov, was a Russian national born in Kyrgyzstan.
A message to Russia
The statement from the Imam Shamil Battalion said the bombing served as a message to Russia for its alleged violence against Muslim countries, citing Syria and Libya as well as the Russian republic of Chechnya.
"To the Russian government, which apparently has not taken a lesson from its defeat in Afghanistan, we say: This operation is only the beginning, and what is to come will make you forget it, Allah permitting," the statement read, implying there would be more attacks against Russia in the future.
Russia has been on edge since the attack in St. Petersburg, as it fights a lingering Islamist insurgency in the North Caucasus.
Russian forces have also intervened in the Syrian conflict in support of President Bashar al-Assad, targeting jihadist fighters and others who oppose the Syrian leader.
rs/cmk (AFP, Reuters)
Website With Qaeda Ties Publishes Claim on St. Petersburg Bombing
MOSCOW — A website that has previously carried Al Qaeda messages on Tuesday issued a claim of responsibility for the recent subway bombing in St. Petersburg, Russia, publishing a statement from a previously unknown cell said to be working on behalf of the terrorist group.
Experts urged caution because the website, Agence Nouakchott d’Information, or ANI, is associated with Al Qaeda’s branches in Africa and is not a normal venue for the terrorist group’s claims of responsibility from elsewhere in the world. The claim that appeared on the website was repeated on Al Andalusi, a channel on the messaging service Telegram associated with Qaeda operations in Africa. There was no similar post on Al Qaeda’s main media channel, which on Tuesday posted an audio recording eulogizing one of the group’s fallen leaders.
Russian investigators identified Akbarzhon A. Dzhalilov as the suicide bomber who carried out the April 3 attack, which killed 15 people and wounded at least 60. Security officials at the time said they were unsure whether Mr. Dzhalilov had acted alone, and they detained several other people in connection with their investigation.
The previously unknown group claiming responsibility, the Imam Shamil Battalion, said in its statement that Mr. Dzhalilov had acted on the orders of Ayman al-Zawahri, the leader of Al Qaeda, according to a translation provided by the SITE Intelligence Group, which tracks extremist propaganda. The statement also threatened additional attacks.
“This operation is only the beginning, and what is to come will make you forget it,” the statement said, adding, “If you do not stop your government from interfering in the Muslim countries, you will be the ones paying the price with your own blood, just as our brothers in Syria, Chechnya and Libya are paying.”
Another oddity is the date of the claim, which appears as April 18. Claims of responsibility are quickly picked up and propagated by Al Qaeda, making the delay in this instance suspect.
Mr. Dzhalilov was a native of Kyrgyzstan who had a Russian passport and had lived in St. Petersburg for at least five years before the attack. He worked at a sushi bar and a car repair shop, and he visited Kyrgyzstan regularly.
Earlier in April, law enforcement officers arrested 10 men of Central Asian origin in St. Petersburg and Moscow on suspicion of being involved in preparing the attack. An explosive device was found at one of their apartments that was identical to one left by Mr. Dzhalilov at another subway station and defused by the authorities.
One of the suspects, Abror Azimov, said during a court hearing in Moscow that he had acted on someone else’s commands and did not know that he was participating in a terrorist act, the Russian newspaper Kommersant reported.
The St. Petersburg attack was the first major attack in a large urban center in Russia since twin bombings rocked central Volgograd in 2013.
President Vladimir V. Putin sent the Russian military to Syria in September 2015 in order, he said, to defeat terrorists before they could reach Russia. Critics said, however, that Mr. Putin’s main goal was to prop up President Bashar al-Assad of Syria, his main ally in the Middle East.