BERLIN - German police questioned and then freed a man on suspicion of acting as a contact in the explosion of a truck at a synagogue in Tunisia that killed 15 people, including 10 Germans, prosecutors said yesterday.

The man was let go after officials found no compelling evidence of wrongdoing. However, the Federal Prosecutor's Office said that despite his release, "Indications that the event of April 11 was a terror attack have strengthened."

Two Arab newspapers reported that a group with the same name as one linked to Osama bin Laden's terror network claimed responsibility for the blast on a Tunisian resort island.

The suspect was taken into custody Monday in the western city of Duisburg based on a tip about a telephone call from Tunisia to Germany before the explosion, said Frauke Scheuten, a spokeswoman for federal prosecutors.

He was released yesterday after questioning and searches of his apartment and those of several associates turned up no evidence to warrant holding him longer, prosecutors said.

According to a report in the news magazine Stern, German police eavesdropped on a phone conversation shortly before Thursday's explosion of a gas truck at the Ghriba synagogue on the Tunisian island of Djerba. Either the driver or a passenger in the truck spoke with a contact in Germany who police believe has links to Muslim radicals, the magazine reported.

A spokesman for German federal police, Gerhard Schlemmer, declined to comment on the report or to indicate if investigators had found links between the Djerba explosion and two terror cells in Germany.

"We can't judge that at the moment," he said.

Tunisia's government, which had previously described the synagogue blast as a "tragic accident," confirmed in a statement yesterday that the inquiry was now pursuing other leads, "including the possible links that (the truck driver) could have had with elements established in Germany," the official Tunisian news agency reported.

The statement said the truck driver lived with his family in the French city of Lyon, but didn't identify him further. The statement also mentioned a recent wave of anti-Semitic attacks in France and other countries following the Israeli military offensive in the West Bank.

In frontpage reports yesterday, the London-based pan-Arab dailies Al-Quds Al-Arabi and Al Hayat said they had received a claim of responsibility for the synagogue blast from a group calling itself the Islamic Army for the Liberation of the Holy Sites.

The group, who claimed it was retaliating for "Israeli crimes" against Palestinians, used the same name as a group that claimed responsibility for the 1998 bombings of U.S. embassies in Kenya and Tanzania. That 1998 claim described bin Laden as a "source of inspiration" and referred to him as the "warrior sheik."

Bin Laden's network is accused in the Sept. 11 attack on the United States.

Al-Quds did not say how it received the statement, and its authenticity could not be verified. Al Hayat said the statement was received in its office in Islamabad, Pakistan. Al Hayat said the Arabic statement was on stationery with al-Qaida's logo.

Al-Quds said it also received a will said to have been left by the truck driver.

The U.S. government is investigating claims that the Tunisia bombing was an al-Qaida operation, said a U.S. official, speaking on the condition of anonymity. U.S. officials had suspected terrorism last week.

"It certainly looks as though it's as an act of terrorism," the official said yesterday. "We're looking into the links (to al-Qaida)."

Officials in Tunisia have said the explosion occurred after the truck struck the wall of the synagogue and that the driver was among the dead.

That contrasts with accounts by German witnesses that they saw a man get out of the truck and walk away after it was parked in front of the synagogue.