The organization's humanitarian coordinator claimed that the internally displaced had come to the registration point, considering it a safe haven.
OCHA said that it will temporarily suspend critical services as the security situation is assessed.
The Sherkot registration point in the city of Kohat was the target of Saturday's attack.
More than a quarter million people who fled the fighting in the Orakzai and Kurram agencies are registered as IDPs in Kohat and neighbouring Hangu.
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