A Guardia Civil officer was shot in the leg during an operation targeting drug traffickers in the El Saladillo neighbourhood in Algeciras yesterday.
The officer, whose injuries were not life-threatening, was shot from a balcony as officers inspected a van they suspected was loaded with drugs.
The van had been followed from the Costa del Sol to Algeciras by law enforcement agencies.
A Spanish police spokesman told the Chronicle the person who fired the shots had probably mistaken the officers with for a gang wanting to steal the drugs, a common practice among rival criminal organisations in Spain.
They were dramatic scenes as police and the Guardia Civil deployed numerous officers to the scene, taking cover behind cars and walls as they moved in to arrest the gunman.
When police and Guardia Civil officers searched the residence from where the shots were fired, they found close to three tonnes of cannabis resin inside.
The gunman had fled the scene however and remained on the run as this edition went to press.
The investigation remained open.
In a separate operation, police in La Linea seized three tonnes of cannabis resin in the early hour of Wednesday morning.