Colombia’s anti-government guerrillas have grown stronger under President Gustavo Petro’s three years in office.

An attack on a Colombian National Police helicopter and a suspected car bombing near a military air base left at least 19 people dead Thursday in what Colombian authorities are describing as terrorist acts.

Colombia has been rocked by one of its deadliest coordinated attacks in recent years, leaving at least 17 people dead. Authorities say dissidents of the defunct FARC rebels launched two brutal strikes: a car bomb outside a military aviation school in Cali and a drone attack on a police helicopter in Antioquia.