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Iran has arrested a member of the negotiating team that reached a nuclear deal with world powers on suspicion of spying, a judiciary spokesman said on Sunday, according to the Reuters news agency.

The suspect was released on bail after a few days in jail but is still under investigation, the spokesman, Gholamhossein Mohseni Ejei, was quoted as having said at a weekly news conference.

He called the unidentified individual a "spy who had infiltrated the nuclear team," state media reported.

Ejei was responding to a question about an Iranian lawmaker's assertion last week that a member of the negotiation team who had dual nationality had been arrested on espionage charges.

Tehran's prosecutor general on August 16 announced the arrest of a dual national he said was linked to British intelligence, but made no mention of the person being in the nuclear negotiations team, noted Reuters.

On Sunday, Ejei did not explicitly confirm that the arrested person had a second nationality, though Britain said on August 16 that it was trying to find out more about the arrest of a joint-national.

Earlier this month, Iran announced it had executed a nuclear scientist convicted of handing over "confidential and vital" information to the United States.

Iran has in the past executed people it claimed to be “spies” for both Israel and the U.S.

In June of 2012, Iran claimed to have dismantled a terrorist and sabotage network in the southern city of Shiraz, which allegedly planned bombings and assassination attempts during Iran’s presidential election.

The network had links with the CIA, Israel and some neighboring Arab nations, Iran claimed.

A month earlier, Iran hanged two convicted spies, one accused and found guilty of working for Israel, the other for the United States.

In a previous incident, Iran executed Majid Jamali Fashi after convicting him of spying for the Mossad and of playing a key role in the January 2010 assassination of a top nuclear scientist in return for payment of $120,000.