ST. PETERSBURG, April 4. /TASS/. The signs of a terror attack in St. Petersburg metro blast are obvious, though a final qualification is yet to follow, according to Kremlin spokesman Dmitry Peskov.

"From the legal point of view, we cannot yet say it was a terror attack. Investigators will be able to say that after they consider all the theories," he said. "Signs of a terrorist attack are obvious but there are certain investigation procedures. So, we must wait until investigators qualify the blast this way," he added.

Peskov also said a suicide bomber theory of the subway blast is to be commented by investigators. "It is in the competence of investigative agencies," he said when asked to comment on reports about possible involvement of a suicide bomber.

According to Peskov, President Vladimir Putin held a meeting with security and law-enforcement services on Monday where he was informed about preliminary results of the investigation over the metro blast. "President has been informed about the preliminary results of the initial investigation," Peskov said.

"Currently President is almost constantly provided with the latest update by security services and investigation bodies. Apparently, tomorrow he will be provided with further information," Kremlin spokesman said, adding that "all efforts are used through both city authorities and federal bodies to assist injured and the families of those killed."

Peskov reported later that President of the United States Donald Trump called Putin to extend condolences after the blast in St. Petersburg. "In a telephone conversation with Vladimir Putin Donald Trump extended deep condolences to the families of those who were killed in a barbaric terror attack in St. Petersburg subway, and asked to pass on words of encouragement to the Russian people," Peskov said. "Presidents consider terrorism to be an evil that should be tackled in a concerted effort," he said, adding that Putin and Trump have "agreed to keep in touch."

An unidentified device went off at about 14:40 Moscow time on Monday in a subway train car when the train was moving from Tekhnologichesky Institut Station to Sennaya Ploshchad Station. The Russian Investigative Committee has qualified the blast as a terrorist attack, but other versions are looked into.

According to the latest data provided by the National Anti-terrorist Committee, the blast claimed 11 lives.