An unnamed Chinese warship allegedly challenged an Indian navy vessel as it left a Vietnam port on July 22.

According to the Financial Times, the Chinese craft insisted the Indian amphibious assault vehicle, the INS Airavat explain its presence in Chinese waters.

Indian officials claim the ship was 45 miles off the Vietnamese coast, well within Vietnam's economic zone.

India's senior foreign ministry spokesman told the FT that the Airavat was "contacted on open radio channel by a caller identifying himself as the 'Chinese Navy' stating that 'you are entering Chinese waters'".

The Airavat did not see any aircraft or ships in the area.

While China claims the entire South China Sea as its own, an Indian official familiar with the incident says, "Any navy in the world has full freedom to transit through these waters or high seas. For any country to proclaim ownership or question the right to passage by any other nation is unacceptable."

Vietnam has acknowledged the Airavat was docked in the country from July 19-22, but has released no information on the incident.

China defense and foreign ministries deny the incident as well.