TEHRAN - Iran warned Germany on Tuesday against trying to pressure the Islamic state into freeing two German reporters detained while interviewing the son of a woman sentenced to be stoned to death for adultery.

Iranian Foreign Ministry spokesman Ramin Mehmanparast issued the warning after 100 German political and business leaders published an appeal to Iran on Sunday to free the two German reporters held in Iran since October.

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"We inform our German friends that the strategy of creating pressure to influence the court decision will have the opposite effect," Mehmanparast told a weekly news conference.

"We are warning that our judiciary will never make decisions under such pressures ... Our judiciary is independent."

The two reporters for German weekly Bild am Sonntag were arrested while interviewing Sajjad Ghaderzadehson, the son of Sakineh Mohammadi Ashtiani, a woman sentenced to death for adultery. Her case has sparked global outrage and highlighted concerns about Iran's human rights record.  

German Foreign Minister Guido Westerwelle was among members of Chancellor Angela Merkel's cabinet to join opposition leaders and celebrities in the appeal, published over 15 pages in Bild am Sonntag.

Iran says the German reporters did not have permission to work as journalists in the country.    

Ashtiani, jailed in the northwestern city of Tabriz, told reporters on Saturday that she had asked her son to sue the Germans for "embarrassing" her.