The picture shows that a policeman and firemen stand outside the metro station where a blast went off in St. Petersburg, Russia on April 3, 2017. Two subway stations were hit by explosions with destructive elements and so far at least 10 people have been killed. (Xinhua/Sputnik Photo)

UNITED NATIONS, April 3 (Xinhua) -- UN Secretary-General Antonio Guterres on Monday condemned the bombing in St. Petersburg subway, which killed at least 10 people, saying that those responsible for the attack should be held accountable.

"The secretary-general condemns today's bombing in the St. Petersburg metro," UN spokesman Stephane Dujarric said at a daily news briefing here.

"He extends his deepest sympathy and condolences to the families of the victims and to the government and the people of the Russian Federation," Dujarric said. "Those responsible for this appalling act must be held accountable."

The blast took place on a subway train in the Russian city of St. Petersburg Monday afternoon, killing at least 10 people and injuring about 50 others, a report said.

The bomb, a homemade device filled with shrapnel, exploded in the third car just after the front of the train had entered the tunnel, the report said.