Mexican navy says that federal police opened fire on a US embassy vehicle carrying two US government employees, after the vehicle entered an area where the Mexican officers were conducting anti-crime operations.

The two embassy employees were hospitalised, one with a wound to the leg and the other with wounds to the stomach and hand, according to a government official who spoke on condition of anonymity.

The US embassy said it could not release details of the shooting or the names of the victims.

The navy said at least four vehicles opened fire on the Americans’ four-wheel drive vehicle on a road south of Mexico City, but did not make clear if any of the four carried federal police officers.

The shootings appeared to have been the result of a confused running gun battle that broke out on a rural road in a mountainous area that has been used by common criminals, drug gangs and leftist rebels.

The navy said the embassy personnel were heading down a dirt road to a military installation when a carload of gunmen opened fire on them and chased them.

A Navy officer was accompanying the embassy employees. The Americans tried to escape, but three other cars joined the original vehicle in pursuing them down the road.

Occupants of all four vehicles opened fire, and the navy captain called for more help. Federal police officers and Mexican army troops then arrived on the scene.

The statement did not make clear whose bullets injured the two workers. The US vehicle appeared to have been armoured and had diplomatic plates.

The government official said the wounded were not agents of the US Drug Enforcement Administration or the FBI, but did not identify which agency they work for.

“We are working with Mexican authorities to investigate an incident this morning in which two employees of our embassy in Mexico City came under attack by unknown assailants,” said Victoria Nuland, a State Department spokeswoman in Washington.

The embassy vehicle was riddled with bullets, most concentrated around the passenger-side window, indicating the possible involvement by experienced gunmen.

The scene of the shooting was cordoned off and guarded on Friday by more than 100 heavily armed marines and soldiers. The highway was closed.

Investigators examined what appeared to be shell casings left at the scene.