German Bild am Sonntag newspaper launched a high- profile campaign on Sunday, appealing for the release of two of its journalists detained in Iran, dpa reported.
The men - a reporter and a photographer - were arrested on October 10 in north-western Iran while interviewing the son of Sakineh Mohammadi-Ashtiani, a woman sentenced to death by stoning for murder and adultery.
Bild am Sonntag, the Sunday edition of Europe's best-selling newspaper, wrote on its front page, "We are greatly concerned over two colleagues."
The reporters were initially accused of not having proper accreditation, after entering Iran on tourist visas. However a provincial justice chief has since accused them of espionage, which would carry more serious consequences.
The newspaper said it decided to launch a public appeal after the reporters were shown on Iranian state television earlier in the week, apparently admitting to their wrongdoings.
Bild am Sonntag's chief editor Walter Mayer wrote in an editorial that it pained them to see the TV images of their colleagues.
"We see that they are doing badly, that they are suffering," Mayer wrote, appealing, "Both must come home soon!"
On Friday, German Foreign Minister Guido Westerwelle called on Iran to respect international law in its treatment of the journalists, including regular consular access and "appropriate custodial conditions."