BOGOTA (AFP) - Colombian authorities have arrested a woman who is suspected of arranging the murder of four boys who were shot to death execution-style in their home, the local prosecutor's office said.

In a case that has shocked the country, the four siblings - ages four to 17 - were each killed with a single bullet to the head in the town of Florencia, 370km south of Bogota.

Their parents had gone to enroll them in school, leaving them alone in the house.

Their bodies were found on Feb 5.

A fifth boy, aged 12, was wounded but survived the shooting.

On Monday, authorities announced the arrest of Luz Mila Artunduaga, described as a companion of a man involved in a land dispute with the parents of the murdered children.

Prosecutors allege that Artunduaga planned the murders, apparently driven by a desire for revenge against the parents.

On Saturday, two men were arrested on suspicion of carrying out the actual killings, along with a brother of one of the two.

Colombia's public defender, who is tasked with protecting human rights, says 1,115 minors were murdered in the country in 2013, the latest year for which statistics are available.