TEHRAN, Iran - Iran on Tuesday accused two detained Germans of having links to Iranian exile groups after they were arrested reportedly while trying to interview the son of a woman sentenced to death by stoning for adultery.

The stoning sentence against the woman, Sakineh Mohammadi Ashtiani, raised an international outcry, embarrassing Tehran. The arrest of the two Germans suggested how sensitive the government is over the case -- and the claim that they are connected to Tehran's bitter opponents abroad raised the possibility they could face future security-related charges.

In Berlin, the German Journalists' Association said the two Germans are journalists -- a reporter and a photographer -- who were interviewing Ashtiani's son, Sajjad Qaderzadeh, when they were arrested on Sunday. The union also did not name the journalists.

But Iranian Foreign Ministry spokesman Ramin Mehmanparast, confirming the arrests, said Monday that "it is not clear whether they are journalists."

He said the two Germans were arrested as they approached Ashtiani's house in the northwestern Iranian city of Tabriz. The 43-year-old mother of two is in prison in Tabriz, waiting for the judiciary to decide her fate. The son apparently lives in his mother's home.

"Since they had links with foreign-based counterrevolutionary networks, they were arrested and the case is under review," Mehmanparast added. He said an Iranian anti-government group that "facilitated the interview is based in Germany." Many exiled Iranian opposition groups have offices in Germany.

The whereabouts of Qaderzadeh and his mother's lawyer, Houtan Kian, were not immediately known and their cellphones have been switched off since the Germans' arrest, possible indications that they too are in custody.

The woman at the centre of the stoning case, Ashtiani, was first convicted in May 2006 of having an "illicit relationship" with two men after the death of her husband -- for which a court in Tabriz sentenced her to 99 lashes. Later that year she was also convicted of adultery, despite having retracted a confession, which she claims was made under duress. She was sentenced to death by stoning for the adultery conviction.

After an international uproar over the sentence, Iran temporarily suspended the stoning verdict against Ashtiani, but says no definite decision has yet been made about her case.

The Germans' arrests will almost certainly elevate tensions between Iran and the West, already running high over suspicions about Tehran's nuclear ambitions.

German Chancellor Angela Merkel said her government was seeking their release.

"We have a great interest in the two citizens being freed," Merkel said during a visit to Bucharest, Romania. "The Foreign Ministry is doing everything within the range of our capabilities."

German Foreign Minister Guido Westerwelle said during a visit to New York that he had asked his Iranian counterpart to take care of the case personally and that a team from the German Embassy would go to Tabriz to try to see the detainees, the German news agency DAPD reported.

Iran has also been holding two American men in prison for 14 months, adding to strains with the U.S.

Tehran initially said the two Americans crossed the border illegally from Iraq but later charged them with spying. The U.S. government and their families say the two were innocent hikers and if they strayed across the border, it was inadvertent.

Mehmanparast said it was up to Iran's powerful, hard-line judiciary to explain where the two Germans are being held. The judiciary said Monday only that it arrested two foreigners who had entered the country on tourist visas and did not have documents to prove they were journalists.

A spokesman for the German Journalists' Association demanded their release.

"One has to see that freedom of press does not exist in Iran, that is extremely dangerous for foreign journalists to carry out critical reporting there," Hendrik Zoerner told AP Television News on Tuesday.

There are only a handful of Western journalists still allowed to work in Iran, and authorities can abruptly withdraw their accreditation.

Leading Spanish daily El Pais said Monday its correspondent in Tehran, Angeles Espinosa -- one of the paper's top foreign reporters-- had her residency permit cancelled Sunday and was given two weeks to leave the country. She has been posted there for the past five years.

El Pais says Espinosa was detained in July after interviewing Ahmad Montazeri, son of a late dissident cleric. Back then she had her press pass taken away but was led to believe she would get it back after the summer holidays. But on returning to Tehran, authorities took away her passport for three weeks. They returned the passport Sunday but with residency permit cancelled and an order to leave Iran.