The father of the Turkish-born man suspected of killing three people in an attack Monday in the Dutch city of Utrecht said his son should be punished if found responsible, a Turkish news agency reported.
Pieter-Jaap Aalbersberg, the national coordinator for counterterrorism and security, said the threat level in Utrecht has been raised to Level 5, the highest level, and a "terrorist motive is not excluded".
Anti-terror police and three emergency helicopters rushed to the scene shortly after, but it is not yet known how many people have been taken to hospital.
Several people were injured Monday in a shooting on a tram in the Dutch city of Utrecht, authorities said, an attack they said could be connected to terrorism. "A terrorist motive can not be excluded", Mr Rutte said. "We think there is just one perpetrator, but we can not exclude the possibly of there being several perpetrators".
Police have arrested Gokmen Tanis, a 37-year-old Turkish man, in connection with the shooting.
Local media reported that ambulances rushed to the area around the incident, near the 24 Oktoberplein, a busy intersection in southwest Utrecht.
The mayor of Utrecht, Jan van Zanen, said three people had been killed and nine injured, three of them seriously, in the tram incident.
No arrests have been made and the gunman is understood to still be at large.
Local sources told Daily Sabah that the Dutch police are taking additional security measures at Amsterdam's Schiphol International Airport and in front of mosques throughout the country.
Police could not immediately provide further details about the shooting incident and could not say how badly hurt the victims were. He did not rule out the possibility that more than one person was involved.
Utrecht University has closed all of its buildings and trains are not allowed to run into the city's central station. This is a shooting incident in a tram.
The Netherlands' fourth-largest city was on lockdown.
Police in the Netherlands have released a photograph of suspected gunman Gokman Tanis following the deadly attack on a tram in Utrecht.