Law enforcement agencies had support from a helicopter when they swept high-crime areas of the capital Friday night and Saturday morning.
Targeted were Parque Central, Parque la Merced and the Plaza de la Democracia in downtown San Jusé, the Los Guido section of Desamparados, Los Cuadros, Purral, Ipís, Rincón Grande in Pavas and León XIII.
Searches turned up eight illegal firearms, said the security ministry.
Participating in the sweep were members of the Grupo de Apoyo Operacional of the Fuerza Pública, the Servicio de Vigilancia Aérea in the helicopter, the Policía Municipal in San José, the Unidad Canina, the Judicial Investigating Organization and the Policía de Tránsito.
The ministry said that 17 motorcycles and a car were impounded. In all, eight persons were detained, the ministry said.
One was a 16 year old who faces allegations of resisting police and attempted robbery. He had to be taken out of a private home where officers confiscated two firearms.
Four persons were detained for robbery of a minor. The ministry said they used a choke hold to effect the crime. This is known as the candado chino in Costa Rica where the assailant cuts off the blood flow at the neck until the victim passes out.
The new helicopter is of a type that creates less noise, and it was purchased to provide support for such sweeps, the ministry said.