The Palestinian armed group's Qatar-based chief negotiator replaces Yahya Sinwar, who was killed by Israeli forces in Gaza in 2024.
A senior officer in the Hamas-run police force was among those killed in the strike, which Israel's military says targeted "terrorists".
Khanna, 49, was visiting the occupied West Bank when he was held for 90 minutes, he says.
The lawyer for Dr Hussam Abu Safiya tells the BBC his client was so badly beaten he could not recognise him during a visit last week.
Israel's police force says the officer acted "not in accordance with procedure" and that it has opened an investigation.
An estimated 300 Palestinians referred for treatment abroad have died since the ceasefire began, according to Gaza's Hamas-run health ministry.
Israel rejects the new report by the three-member expert panel, calling it a "libellous sham".
Israeli nationalists are increasingly flouting a convention on how faiths share the al-Aqsa mosque compound.
Demonstrations took place on Sunday at a synagogue where the property sales event was being held.
