German Foreign Minister Guido Westerwelle on Thursday said that the International Criminal Court should examine the use of chemical weapons in Syria.

"I have again pressed for the U.N. Security Council to give a mandate to the ICC to examine the chemical attack in Syria," he said on the sidelines of the G20 summit in Russia's Saint Petersburg.

German intelligence believes the Syrian regime was behind last month's chemical attack but that the large death toll may be the result of a dosage "mistake", news site Spiegel Online has reported.

Spiegel cited secret briefings to lawmakers reportedly given by the director of Germany's BND foreign intelligence service, Gerhard Schindler.

Less than three weeks before German elections, Chancellor Angela Merkel maintained a strong lead in a poll published Thursday, the first taken fully since the campaign's only TV debate.

Despite a spirited performance by her Social Democratic rival Peer Steinbrueck before more than 17 million television viewers last Sunday, his personal approval rating notched up only slightly.

A German aid worker held for almost four months has escaped his kidnappers in Syria, just like his two colleagues who managed to flee in July, their aid group announced on Wednesday.

Engineer Ziad Nouri "is free" and managed to cross the Syrian border into Turkey on Tuesday, the Gruenhelme non-governmental organization said in a statement.

The German office investigating Nazi war crimes said Tuesday it would send files on 30 former Auschwitz death camp personnel to state prosecutors with a recommendation to bring charges.

In a twilight bid for justice nearly 70 years on, chief investigator Kurt Schrimm said the former Auschwitz guards now aged up to 97 should face charges of accessory to murder.

France on Tuesday urged its European Union partners to unite in response to the Syria crisis, as Paris pushes for punitive military strikes against Bashar Assad's regime.

"Europe must also unite on this issue. It will do so, each with its own responsibility. France will assume its own," President Francois Hollande said during a joint press conference with German counterpart Joachim Gauck.

German Chancellor Angela Merkel will come face-to-face in a television clash Sunday with her center-left election rival, confronting Peer Steinbrueck whom she has studiously ignored on the campaign trail.

In what has been billed as the primetime TV event of the year, Steinbrueck will have a last-ditch chance to close a yawning poll gap against the popular Merkel.

German Chancellor Angela Merkel hit out at Russia and China over their stance in the Syrian crisis, saying in an interview published Saturday that their action weakened the United Nations.

"It is very regrettable that Russia and China have refused for some time to come to a common position (with Western partners) on the Syrian conflict. This considerably weakens the role of the United Nations," she said in an interview with regional daily Augsburger Allgemeine.

Germany on Friday ruled out participating in possible strikes against Syria over alleged deadly chemical weapons attacks.

"We have not considered it and we are not considering a military strike," government spokesman Steffen Seibert told reporters, adding that in any case, Berlin has not been asked to take part in any such military action.

U.S. President Barack Obama on Thursday spoke with German Chancellor Angela Merkel about the situation in Syria, the White House said, as the West weighs military action against Damascus.

"The president today conducted a phone call with German Chancellor Angela Merkel. This is part of the series of communications that the president has initiated around the situation in Syria," spokesman Josh Earnest told reporters.