At least three people, including two policemen, were killed in northern Mexico when a car drove into two police vehicles in retaliation for the arrest of a drug cartel boss, the Security Ministry said.
Bystanders in Ciudad Juarez on the US border said they heard an explosion and the ministry said two police officers and a paramedic were killed.
Images showed a badly damaged police pickup truck and scores of police running through the streets.
The attack on the police vehicles was in retaliation for the arrest earlier in the day of Jesus Armando Acosta Guerrero, an alleged senior member of the Juarez drug cartel, the ministry said in a statement.
Drug killings have spiraled across Mexico since President Felipe Calderon launched his military-backed drug war after taking office in 2006.
In Ciudad Juarez, almost 6,000 people have died in drug violence since January 2008.