Seven police officers were murdered when their car struck a roadside bomb before gunmen arrived.
The explosion occurred while the officers were leaving a social function in the south-west Huila area of Colombia.
According to a police spokeswoman, they were then gunned down in an ambush strike.
The murder is the worst attack on security forces since President Gustavo Petro was inaugurated as the country's first left-wing leader last month.
According to local media and the attorney general's office, three of the deceased cops were under the age of twenty.