GENEVA - UN human rights chief Navi Pillay said on Friday she was concerned by reports of the detention of leading members of Egypt's Muslim Brotherhood, but stopped short of saying whether their overthrow this week constituted a coup d'etat.

"I hope that the rule of law and a system of government that respects the human rights of all Egyptians - men and women - can be quickly re-established," she said in a statement.

Her spokesman Rupert Colville told a regular UN briefing that specific crimes would need to have been committed to justify the detentions of the Muslim Brotherhood's leaders.

"We don't really know the details and what the basis of these detentions is. Obviously if you detain or arrest someone there needs to be, according to the law, a very good reason to do so," he said. "There needs to be due process."

Asked if Egypt's new rulers should make clear why the figures were being detained or release them, he said: "I think that's a perfectly reasonable interpretation."

Pillay said Egypt should seize the chance to become a fully functioning and prosperous democracy, but did not condemn Egypt's military for overthrowing President Mohamed Morsi, whose policies she had frequently criticized.

"As you know, globally there's a huge debate going on about whether this was a coup or not a coup or what it is exactly. We're not getting into that," Colville said.

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