UPDATE - Explosion hits St. Petersburg metro

UPDATES WITH FURTHER REACTIONS

By Diyar Guldogan and Hakan Ceyhan Aydogan

ANKARA/MOSCOW (AA) - At least nine people were killed and 20 others injured Monday when an explosion hit the St. Petersburg metro, Russia's National Anti-terrorism Committee (NAK) said.

According to the NAK, the blast tore through a train at 2.40 p.m. local time (1140GMT) as it was traveling between Sennaya Ploshchad and Technological Institute stations.

The initial reports had put the death toll at 10, adding 50 others were injured during the incident.

An explosive device has been found and deactivated at Vosstaniya Ploshchad metro station, the NAK added.

President Vladimir Putin expressed his condolences to the families of those killed and injured during the explosion, the Kremlin said in a statement.

Putin instructed the city authorities to take "all necessary" measures to help the families of the victims.

"The investigation is ongoing. Of course, we always consider all scenarios, including accidental or criminal action, and above all, those of a terrorist nature," he said.

Putin said the ongoing investigation will "soon" provide answers regarding the causes of the "tragedy".

Aleksander Kurennoi, spokesman for the Prosecutor General’s Office, said an investigation had been launched into the blast, which he called a "terrorist attack".

Prime Minister Dmitry Medvedev also conveyed his condolences following the explosion. Medvedev said in a statement that Health Minister Veronika Skvortsova was ordered to take "additional" steps to provide injured people with medical assistance.

Meanwhile, Russia announced a three day mourning after Monday's explosion effective as of Tuesday.

- World reactions

Turkish Prime Minister Binali Yildirim extended his condolences to Medvedev over the explosion, and wished a "speedy" recovery to the injured, according to a prime ministry source, who asked not to be named due to restrictions on speaking to the media.

"I strongly condemn the heinous attack in St.Petersburg that claimed many lives. Condolences to the Russian people," Turkish Foreign Minister Mevlut Cavusoglu tweeted.

Turkish Foreign Ministry said in a statement it was learned with "sadness" that many lives were lost during the explosion.

"As a country that has expressed its stance against all forms of terrorism on numerous occasions, we strongly condemn this heinous terrorist attack," it added.

The ministry also extended condolences to the "friendly" Russian nation.

NATO's Secretary General Jens Stoltenberg tweeted: "Deepest sympathy to those affected by the #StPetersburg metro explosion, their loved ones and the Russian people."

"Following the news coming from #SaintPetersburg, together with all EU Foreign ministers. Our thoughts are with all people of #Russia," EU foreign policy chief Federica Mogherini said at her Twitter account.

U.K. Foreign Secretary Boris Johnson said he was "horrified" by the news of explosion. "My sympathies are with the victims and their families," Johnson tweeted.

Secretary General of the Council of Europe Thorbjorn Jagland said he was "shocked and saddened by the news of deadly blasts in St. Petersburg."

"I extend my sincere condolences to our member state Russia," Jagland tweeted.

Greek Foreign Ministry said in a statement that it was "shocked" by the "deadly" blast in St. Petersburg.

"Greece stands by the Russian people and their government, sends sincere condolences to the families of the victims and wishes a speedy recovery to those wounded," it added.

* Hajer M’tiri from Paris, Idyli Tsakiri from Athens contributed to this story.