Three men and a woman were killed while traveling on an inter-city bus in northwestern Honduras, police said.

According to witness accounts, unknown assailants riding in another vehicle drove up alongside the bus and opened fire at the four people, a National Police spokesperson said.

The victims have not been identified but one apparently had a criminal record and had just left the prison in the city of San Pedro Sula after visiting an inmate, the spokesperson said, adding that the incident occurred around 4:00 p.m. Wednesday.

At least 15 violent deaths occur in the Central American country daily, figures compiled by human rights groups show.

Honduras's 2011 homicide rate of 92 per 100,000 people was one of the highest in the world, a recent U.N. report said. EFE