A group of unidentified armed assailants opened fire on 10 National Police officers yesterday while the officers were responding to a 911 emergency call in Tilarán, Guanacaste, in north-central Costa Rica, the Public Security Ministry said.

Ministry press officer Carlos Hidalgo told The Tico Times none of the officers was hurt in the assault. Police were still in pursuit in the afternoon and had not informed headquarters of any further details.

Tilirán Delegation Commissioner Luis Antonio Mendoza could not be reached yesterday.

The daily La Nación reported local residents claim spotting the assailants carrying large firearms, including an AK-47 assault rifle, but the law-enforcement authorities could not confirm this.