Germany condemns Turkish offensive as violating international law
"We don't believe that an attack on Kurdish units or Kurdish militia is legitimate under international law," Heiko Maas told Germany broadcaster ZDF.
"If there is no basis in international law for such an invasion, then it can't be in accordance with international law," he said, in his strongest comments yet on the assault.
Ankara launched a cross-border attack against Syria's Kurds on October 9 after the United States announced a military pullout from the north of the war-torn country, to widespread international criticism.
NATO member Turkey has justified the offensive as necessary to secure its borders.
A US-brokered ceasefire was announced late Thursday, giving Kurdish forces until Tuesday evening to withdraw from a buffer area Ankara wants to create inside Syrian territory along its southern frontier.
On Sunday, Kurdish-led Syrian Democratic Forces fully withdrew from a Turkish-encircled town in northern Syria, in what appeared to be the start of a wider pullout under the ceasefire deal.
"We will do everything we can to ensure that this ceasefire lasts longer than five days and puts a halt to the invasion for the time being," Maas said.
Germany, along with a string of other European countries, has suspended arms exports to Turkey over the offensive.
Turkish-led bombardment and fire since October 9 has killed 114 civilians and displaced at least 300,000 people, according to the Syrian Observatory for Human Rights war monitor.
More than 250 SDF fighters - the de facto army of Kurdish authorities in northeastern Syria - and 190 pro-Ankara fighters have lost their lives over the same period, it says.