RIO DE JANEIRO (AP) — Rio de Janeiro’s police on Wednesday killed four people who attacked security forces as they were carrying out an operation to contain the advance of the notorious criminal gang Red Command in a sprawling urban community, officials said.

The state’s civil police said it had been verifying intelligence and strengthening ongoing investigations in the Salgueiro complex of favelas, across the bay from Rio.

“During the operation, four criminals attacked the agents and were neutralized in a confrontation,” police said in a statement.

Police also seized four rifles, six pistols, one revolver, two replica pistols, a large quantity of ammunition, drugs, camouflage clothing and radios.

In a separate statement, police said a helicopter was flying over an area near Salgueiro when it was hit, leaving one person injured.

Attacks on the civil police’s armored aircraft have drastically increased in recent years, the institution said, adding that such actions are the “modus operandi of criminal factions, which open fire to prevent the presence of security forces near communities.”

To prevent other people becoming victims, the institution aims to “combat these narco-terrorists,” police said, referencing a term used by U.S. President Donald Trump to designate drug-traffickers.

Red Command has increased its control over favelas in recent years and also spread across Brazil, including in the Amazon rainforest.

Last October, Rio’s most lethal police raid killed more than 120 people, including five police officers. The record toll sparked protests and calls from the left and human rights organizations for reform of the city’s security forces.