Bogota, Colombia:
Three soldiers were killed in an explosion in northern Colombia, defense officials said on Thursday, without identifying the culprits.
The attack took place Wednesday in Norte de Santander, a department bordering Venezuela that is home to several different illegal groups.
A patrol came under attack with improvised explosive devices, a defense ministry statement said.
"Three soldiers were killed and another severely wounded," it added.
The ministry said a police officer was killed in a separate incident this week in the western department of Cauca.
"Indiscriminate terrorist attacks using improvised, unconventional weapons, murders and systematic attacks against security forces and the civilian population perpetrated by illegal armed groups are serious violations of international human rights," the defense ministry said.
Colombia has been battling for half a century a civil war pitting the army against guerrillas, paramilitary militias dissolved since 2006 and criminal gangs. Several hundred thousand people have died in the conflict.
The government of President Juan Manuel Santos has been engaged in talks for the past 19 months with the Revolutionary Armed Forces of Colombia (FARC) in Cuba and recently made official a process of dialogue with the National Liberation Army (ELN).
Founded in the 1960s, the ELN and FARC are the last guerrillas still active in Colombia, where they number 2,500 and 8,000 fighters respectively.