There was an explosion in the southern Russian city of Rostov-on-Don early on Thursday, and one person was hurt, a law enforcement source told TASS news agency. REN-TV cited witnesses as saying that the explosion happened near a school on Sadovaya Street and that a maintenance worker was injured in the blast. This attack came after Monday's deadly St. Petersburg metro bombing that was carried out by a suicide bomber who is originally a Russian citizen living in Kyrgyzstan. The death toll in St. Petersburg metro attack increased to 14 dead, while others are injured among them 4 in a critical condition. It is still unknown until now whether the suicide bomber was dead in the attack or not, but authorities was able to identify him after hours from the incident.