Palestinian authorities said a grave site discovered at the Nasser hospital, the main medical facility in central Gaza, contained nearly 400 bodies
The suicide blast rocked the airport shortly after Afghan Vice President Abdul Rashid Dostum returned to the country after more than a year in exile. Militant group Islamic State claimed the attack.
The Pakistan Foreign Ministry expressed the "deepest sympathies and heartfelt condolences to the families and friends of those who have lost their lives".
"We express our support and solidarity with the people and government of Afghanistan in this hour of grief," the ministry's spokesman said in a statement.
He said Pakistan reiterates its condemnation of terrorism in all forms and manifestations and the resolve to eliminate this menace.