Mexico City - A group of armed men blew up an ambulance Friday, apparently with a grenade, to kill a rival who was being transferred from one hospital to another, officials said.

The state attorney general's office in the western Mexican state of Michoacan said the ambulance had just left the Hospital Civil in the town of Uruapan to take a 24 year- old-man to a hospital in the Michoacan capital Morelia, about 300 kilometres west of Mexico City.

The man had been injured Sunday in a shootout, allegedly with a rival group.

The attack on the ambulance happened at around 2 am (0700 GMT) Friday. The attackers, travelling in two vans, blocked passage and forced two paramedics and a driver accompanying the injured man on the ambulance to leave the vehicle and get away from it, state attorney spokesman Victor Arrendondo told the German Press Agency dpa.

The paramedics and the driver who had been travelling on the ambulance said that as they pulled away they heard shots and then saw the ambulance catch fire. Investigators think that the unknown attackers used a grenade before driving away.

The wife of the injured man - whose body was charred in the attack - was also travelling on the ambulance, and the authorities did not know whether she managed to escape or whether she was kidnapped by the attackers.

Over 3,000 people have been killed since January in incidents linked to organized crime. Last year the figure reached a record of 6,290 drug-related killings.(dpa)