An aircraft known or believed to be in state of emergency, including being subjected to unlawful interference, be given priority over other aircraft.

Unlawful interference
whenever there is any indication of the occurance of unlawful interference with an aircraft, should be handled in accordance with the procedures contained in Doc. 4444-ICAO.

Emergency descent
upon receipt of advise that an aircraft is making an emergency descent through other traffic, all possible action should be taken immediately to safeguard all aircraft concerned. when deemed necessary, ATC unit should immediately broadcast by means of the appropriate radio aids, or if not possible, request the appropriate communication stations immediately to broadcast an emergency message.

note: its is axiomatic that aircraft that experiencing emergency is not able to be instructed to climb, maintain level or other unecessary manouevre. thus the only manoeuvre can be done is subject to the pilot decision.