TEHRAN, Iran - Iran's general prosecutor says two Germans who were arrested while reportedly trying to interview the son of a woman sentenced to death by stoning have admitted breaking the law by entering the country without the proper visas, a local news agency reported Friday.

The stoning sentence against the 43-year-old woman, Sakineh Mohammadi Ashtiani, has raised an international outcry, embarrassing Iran. The arrest of the two Germans -- whom Tehran has accused of having links to Iranian exile groups -- suggests how sensitive Iran is over the case.

Iran's top state prosecutor, Gholam Hossein Mohseni Ejehei, told the semiofficial Fars news agency late Thursday that the Germans have admitted to working as reporters in the country without the required journalist visas.

"The two German nationals have confessed to their offence," Ejehei was quoted as saying. He said the Germans acknowledged that working without the proper visas violates Iranian law.

Foreign reporters need a journalist visa to work in Iran legally.

Ejehei said the pair entered the country on tourist visas and contacted Ashtiani's family in the northwestern city of Tabriz, posing as reporters "without (providing) any evidence" that they were indeed journalists.

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

In Berlin, German Foreign Ministry spokesman Dirk Augustin said he couldn't confirm reports that the two had admitted to visa violations, because "we ourselves haven't yet been able to speak" with them.

He added that Foreign Ministry and the embassy in Tehran are still dealing "intensively" with the case, "and we are practically constantly in contact with the Iranian authorities on the matter."

Earlier this week, the German Journalists' Association said that 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 did not name the journalists.

Iran's Foreign Ministry spokesman Ramin Mehmanparast has said that a German-based Iranian anti-government group had arranged for Germans to interview Ashtiani's family. Many exiled Iranian opposition groups have offices in Germany.

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 Tehran says no definite decision has yet been made about her case.