The bomb that detonated on a rail track as an express train was passing last week could have derailed two trains if the Nevsky Express hadn't been running a minute late, a Russian emergencies official has said.

The train travelling from Moscow to St. Petersburg was partially derailed by the blast on November 27. Twenty six people were killed.

"Things could have been much worse. At that moment, two trains were to pass by each other - the Nevsky Express and the ER-200. The Nevsky Express was one minute late, or three kilometers off, given its speed," Leonid Belyayev of the St. Petersburg emergencies department said on Wednesday.

"If the two trains had met, the tragedy could have been worse," Belyaev said.

Investigators have said Friday's attack, which killed 26 people and injured over 90, bore the hallmarks of Islamist terrorism.

ST. PETERSBURG, December 2 (RIA Novosti)