BOGOTA:  Three women were killed and nine wounded after an explosive device detonated in a restroom in a busy upscale shopping center in Colombia's capital on Saturday. The Andino shopping mall in an exclusive area of Bogota was evacuated after the blast, which occurred around 5 pm local time (2200 GMT) in the women's toilet. The commercial center was packed with people buying gifts ahead of Father's Day celebrations on Sunday. Police said the device was placed in a toilet bowl in the second-floor restroom. President Juan Manuel Santos denounced the attack and promised to bring those responsible to justice. 'We won't let terrorism frighten us,' Santos said from inside the shopping center. 'Bogotanos should feel safe and protected. We won't let our guard down but we mustn't panic. That's what terrorists want.' One of the victims was a 23-year-old French woman who had been volunteering in a poor area of the city, Bogota Mayor Enrique Penalosa told reporters. Streets surrounding the shopping center were closed and buildings cleared as ambulances raced to the scene and security officials tried to establish who was responsible for the blast. Bomb squad specialists combed the area for additional devices. Photographs on social media showed a woman slumped against the wall in a pool of blood and what appeared to be a shard of metal piercing her back. In front of her was another woman with her leg torn apart above the knee. Another image showed the destroyed toilet cubicle with a blood-splattered handrail and debris strewn over the floor. Santos ordered an investigation into the incident. Security has improved in Bogota over the past decade as police and military increased surveillance and put more armed officials on the streets. At one time all bags were checked at the entrance to shopping malls, but that has been vastly scaled back in recent years. Sniffer dogs still check cars at parking facilities in the capital. A peace accord signed last year with the Revolutionary Armed Forces of Colombia (FARC), the country's biggest guerrilla group, raised confidence bomb attacks might cease. The country's second-largest insurgent group, the National Liberation Army (ELN), in February exploded a bomb in Bogota, injuring dozens of police. The Marxist ELN, currently negotiating peace with the government, in a tweet condemned the attack against civilians. Authorities said there have been threats of attacks in Bogota by the so-called Gulf Clan, a group of former right-wing paramilitary fighters who traffic drugs.