Of the six F-16 fighter jets that Thailand readied to deploy along the disputed border, one of the aircraft fired into Cambodia and destroyed a military target, the Thai army said.

Thailand and Cambodia exchanged heavy artillery fire for a second day on Friday as their worst fighting in over a decade intensified and spread to new areas, despite international calls for a ceasefire.

Thailand’s military fired artillery toward Cambodia as tensions further escalate between the two countries over a century-old border dispute. At least 16 people have been killed in the armed clashes as both sides blame each other for starting the conflict.