Sao Paulo, Jul 22 (IANS): At least 18 persons were killed during a police raid targeting a crime group at the Almao favelas in the Brazilian city of Rio de Janeiro, police reported.

Among the dead were a 50-year-old woman, who was hit by a stray bullet during the raid, and a police officer, police spokesman Ivan Blaz said at a press conference on Thursday.

Four suspects accused of killing police officers were arrested during the operation, in which 400 officers were involved and supported by four helicopters and 10 armoured vehicles, Xinhua news agency reported.

Blaz described the situation in the region as "very tense," saying that the criminal ring had expanded from drug trafficking to robbing cargo trucks entering the city of Rio de Janeiro.

The dragnet aimed to locate and arrest the gang members, who planned to enter other favelas on Thursday to carry out vehicle thefts, Lieutenant Colonel Uira do Nascimento Ferreira of the Special Operations Battalion of the militarised police in Rio said at the press conference.