RIO DE JANEIRO -- At least 25 people, including a police officer, were killed in a shootout on Thursday during an operation against drug traffickers in Rio de Janeiro's Jacarezinho slum, police said.

Suspects tried to escape across rooftops as police entered the slum in armored vehicles and helicopters flew overhead, television images showed. The intense firefight kept residents in their homes.

Three policemen were hit and one died of a head wound in hospital, police said.

Bullets fired during the shootout struck a light rail coach and two passengers were hurt by shattered glass from the broken window, the fire brigade said.

It was the deadliest single police operation in the state of Rio de Janeiro, which has suffered for decades from drug violence in its poor neighborhoods known as favelas.

"This is the largest number of deaths in a police operation in Rio, surpassing 19 at Complexo do Alemão slum in 2007, except we did not lose one of ours in that action," police chief Ronaldo Oliveira told Reuters.

Police said that among the dead in Jacarezinho were leaders of the drug trafficking gang that dominated life in the slum. At least 10 suspects were arrested, they said.

Besides drug trafficking, the gang robbed trucks of their cargo and had hijacked commuter trains earlier this year to steal from passengers.

Reporting by Rodrigo Viga Gaier; Writing by Anthony Boadle; Editing by Daniel Wallis.