Egypt's foreign ministry accused Gaza's Hamas rulers on Saturday of raiding an Egyptian cultural centre in the Palestinian enclave and detaining several Egyptians.
"The foreign ministry strongly condemns and denounces this irresponsible act and demands their release," it said of the Egyptians it claimed Hamas arrested on Saturday morning.
Questioned about the incident, the Palestinian Islamist group said a security investigation was taking place into a Palestinian from Gaza who has Egyptian citizenship.
"At this stage no decision to arrest him has been made," Hamas spokesman Ehab al-Ghossein told AFP.
Palestinian sources said the man in question, Adel Abdel Rahman El-Kahlout, is the head of Gaza's Egyptian cultural centre.
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But the Hamas spokesman insisted Kahlout was "lying when he says that he is the head of the representation of the Egyptian people in Gaza".
A source close to the Egyptian embassy in Ramallah said Hamas security services had interrogated Kahlout about a statement circulating among Egyptians in Gaza in support of General Abdel Fattah al-Sisi, Egypt's military chief.
Hamas's interior ministry said on Saturday evening that Kahlout had been released after questioning.
Relations between Egypt and the Palestinian Islamist movement have sharply deteriorated since the military-led ouster on July 3 of president Mohamed Morsi.
The deposed Islamist leader is now in detention, accused of colluding with Hamas in staging prison breaks and killing policemen during the 2011 uprising that overthrew former Egyptian president Hosni Mubarak.
Egypt's foreign ministry did not specify the number of Egyptians arrested in Gaza, which is under semi-blockade by Israel and Egypt.
In its statement, it expressed it support for Palestinians, but said it would not "forgive" Hamas for arresting Egyptians.