A Boeing 747 cargo aircraft operated by Turkish carrier AirACT skidded off the northern runway at Hong Kong International Airport (HKIA) early Monday, killing two people in a ground vehicle it struck and pushed into the water.

The flight, arriving from Dubai under an Emirates SkyCargo number, broke apart and partially submerged in the sea near the airport's perimeter.

The Civil Aviation Department said preliminary information indicates that the four crew members on board were rescued and sent to hospital, while two ground staff were affected and fell into the sea, and their conditions are pending confirmation, although several reports said both eventually succumbed to injuries.

The aircraft did not indicate any signs of distress on approach at HKIA, the world's busiest cargo hub.

CAD said air traffic control personnel immediately notified the Airport Authority and other rescue units according to the established procedures. 

"An accident occurred at Hong Kong International Airport at around 3.50am today (October 20). A B744 cargo aircraft (flight number UAE9788), arriving from Al Maktoum International Airport, United Arab Emirates, had deviated from the North Runway after landing and ditched into the sea," CAD said in an update.

"The North Runway is closed due to the accident, while the South and Centre Runways will remain operational," it added.

CAD noted that it attaches great importance to the accident and is following up with the relevant parties at the airport, including the airline involved.

It has also reported the incident to the Air Accident Investigation Authority in accordance with the established mechanism and is sparing no effort to support the investigation.

Authorities are still working to determine the cause of the crash, with weather, runway conditions, aircraft performance, and crew actions all under review.

Emirates said in a statement that flight EK9788, a Boeing 747 cargo aircraft wet-leased from ACT Airlines, was damaged during landing at HKIA.

"Crew are confirmed to be safe and there was no cargo onboard," Emirates said.