The German embassy in Beirut had alerted German nationals in Lebanon after receiving a warning from German intelligence services, German newsmagazine Der Spiegel said in a story released in advance of publication on Monday.

The weekly said the security services feared revenge attacks because of the German navy's participation in a UN task force patrolling the Lebanese coast to stop arms supplies reaching Hezbollah guerrillas.

The German commitment "has led to a changed and in some cases hostile attitude by some radical Lebanese movements towards Germany and to Germans living in Lebanon," the magazine quoted an embassy statement as saying.

Officials at Germany's foreign ministry said "isolated cases of hostility or even violence against Germans in Lebanon cannot be ruled out," according to the magazine. Even the embassy itself was a potential target, the report said.

Diplomats had advised Germans to avoid unnecessary travel and to stick to "places that are well-known and secure."

Another reason for the threat was the German police investigation of Lebanese nationals Jihad Hamad and Youssef al-Hajdib, Der Spiegel reported. The pair are suspected of planting suitcase bombs on two trains in Germany last summer. The devices failed to explode.