UPDATE 2 - 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.

Turkish Foreign Minister Mevlut Cavusoglu condemned the "heinous" attack in St.Petersburg. "Condolences to the Russian people," he 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.

U.S. President Donald Trump called the attack a "terrible, terrible thing."

"Happening all over the world. Absolutely a terrible thing," he said during brief remarks in the White House's State Dining Room while meeting with Egytian President Abdel Fattah al-Sisi.

The U.S. Department of Homeland Security said it was "monitoring the situation in St. Petersburg", but said no change had been made to the U.S.'s terror threat level.

UN Secretary-General Antonio Guterres condemned the bombing in the metro and extended his "deepest" sympathy and condolences to the families of the victims and Russian people.

"Those responsible for this appalling act must be held accountable," Guterres said in a statement.

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

EU foreign policy chief Federica Mogherini sent Russia a message of solidarity.

"Following the news coming from #SaintPetersburg, together with all EU Foreign ministers. Our thoughts are with all people of #Russia," she said on Twitter.

German President Frank-Walter Steinmeier said in a statement that he followed the news from St. Petersburg with "horror" and "grief".

French President Francois Hollande condemned the attack and expressed solidarity with the Russian people.

"The exact circumstances of this tragedy will be established within the framework of the investigation which has just been opened for the act of terrorism. This tragic event reminds us of the need for constant vigilance," Hollande said in a statement.

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.

Azerbaijani President Ilham Aliyev said in a statement that he was "deeply" shocked with the incident.

"We strongly condemn any action directed against innocent civilians," said Aliyev.

Kazakhstan’s President Nursultan Nazarbayev conveyed condolences to Putin in a telegram, the presidency said in a statement.

"We are shocked by this tragic news and we sincerely share the pain of loss together with the people of the Russian Federation,” Nazarbayev said.

Kyrgyz President Almazbek Atambayev condemned in a statement the "inhuman" act aimed at "peaceful" and "innocent" citizens.

Uzbekistan's President Shavkat Mirziyoyev extended condolences to Putin in a statement.

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