Security services in Kyrgyzstan say a national of the Central Asian state has been behind an explosion which left over a dozen people dead in St. Petersburg, Russia.

A spokesman for Kyrgyzstan’s security services identified the suspect as “a Kyrgyz national Akbarjon Djalilov... born in 1995,” AFP reported.

“It is probable that he acquired Russian nationality,” the source added.

The Russian Investigative Committee said the deadly St. Petersburg metro blast, which killed 14 and injured almost 50 others, was caused by a bomb that had been detonated by a man whose body parts were found in one of the train carriages.

"It has been ascertained that an explosive device could have been detonated by a man, fragments of whose body were found in the third carriage of the train," the committee said in a statement.

The committee also revealed the identity of the attacker as Akbarjon Djalilov, adding that Djalilov had also planted a second bomb that was defused by the authorities.

"The investigation identified the man who set off the bomb in the carriage of the Saint Petersburg metro. It was Akbarjon Djalilov," the statement said, noting that Djalilov's "genetic trace" was also found on a bag with the second bomb found at a different station.

Speaking to reporters on Tuesday, the Kremlin spokesman described the St. Petersburg metro attack as a "challenge" to all Russians, including President Vladimir Putin.

"Any act of terror that takes place in the country is a challenge to every Russian, including the head of state, including our president," Dmitry Peskov added.

The blast ripped through a subway train traveling between St. Petersburg’s Sennaya Ploshad and Technological Institute stations. The Kremlin has stated that the incident has “all the hallmarks of an attack.”

Following the blast, the city’s metro system was closed down as police found and defused another explosive device in another station.

Foreign Minister Sergei Lavrov has said that the attack highlights the need for joint efforts against global terrorism. "(This tragedy in St Petersburg) once again shows the importance of stepping up joint efforts to combat this evil," RIA Novosti quoted Lavrov as saying on Tuesday.

The deadly incident has been met with reactions from world countries and organizations.

‘Global will needed to end terror’

Condemning the attack, Iran reiterated calls to form a serious international coalition for battling terrorism.

“We believe that the only way to stop these terrible atrocities is to cut them off by the roots; the only way to do this is through serious will of all international governments and organizations,” said Foreign Ministry spokesman Bahram Qassemi.

Hezbollah condemns attack

Separately, the Lebanese resistance movement of Hezbollah also condemned the terrorist explosion in Saint Petersburg. In a Monday statement, Hezbollah said the attack was further reason for world countries to unite in their efforts to confront the terrorists and their financial and ideological sources.

It said the attack would not dent Russia’s determination to fight terror.

United Nations slams deadly Russia blast

Meanwhile, UN Secretary General Antonio Guterres has condemned the attacks, stressing that those behind it must be held accountable.

“The secretary general condemns today's bombing in the St. Petersburg metro," said the UN chief’s spokesman Stephane Dujarric.

"He extends his deepest sympathy and condolences to the families of the victims and to the government and the people of the Russian Federation…Those responsible for this appalling act must be held accountable," he added. The UN Security Council also slammed the bombing as a "barbaric and cowardly terrorist attack."  

Trump calls blast a ‘terrible thing’

US President Donald Trump also slammed the attack while attending an event at the White House. “Terrible. Terrible thing. Happening all over the world. Absolutely, a terrible thing, " he said.

According to the Kremlin, Trump also had a telephone conversation with Russian President Vladimir Putin to offer his condolences.

The US president also conveyed his support for the people of Russia, said a statement released by the Kremlin. It added that both leaders had voiced their joint view that "terrorism is an evil that must be fought jointly."

White House press secretary Sean Spicer also censured the attack, and offered condolences to the families of the victims.   

“Attacks like these on ordinary citizens going about their lives remind us that the world must work as one to combat violence in all forms," said Spicer. "The United States is prepared to offer assistance to Russia and may require investigating this crime."

The acting US State Department spokesperson, Mark Toner, also condemned the “reprehensible attack on passengers of the St. Petersburg metro system.”

“We extend our deepest condolences to the loved ones of those who were killed, and our thoughts and prayers are with those injured in the attack and with the Russian people," he said.

Washington’s UN Ambassador Nikki Haley also stated that pictures showing the aftermath of the attack were "heartbreaking." "You can be sure the United States will stand with Russia on defeating these extremists who continue to senselessly harm innocent people," she said in a statement.

Extremists linked to bombing attack

According to the Interfax news agency, a police official said that the assailant had links to outlawed extremist groups.

He noted that the suspect was probably a 23-year-old man with central Asian heritage, but final conclusions would be made after DNA tests are carried out on the remains at the site.

A man who was earlier thought to have a role in the incident based on security camera footage has presented himself to the police claiming his innocence.