BERLIN (AFP) - German Foreign Minister Frank-Walter Steinmeier warned on Monday that there could be no military solution to the violence in Ukraine and urged progress towards a negotiated settlement of the conflict.

"Even if the situation in eastern Ukraine has shifted in favour of the Ukrainian security forces, there will be no purely military resolution of the conflict," Steinmeier said on a visit to Mongolia according to a statement from his ministry.

The minister called on all sides to keep an agreement to continue talks within the so-called Contact Group representing Russia, Ukraine and the Vienna-based Organization for Security and Cooperation as well as separatist rebels.

Steinmeier noted that a meeting of the Contact Group without the separatists Sunday had by all accounts been "very difficult".

He said the goal should remain the agreement of a ceasefire in eastern Ukraine.

"This essential step to calm the situation must be taken before a political solution can even be considered," he said.

A German government spokeswoman, Christiane Wirtz, later told reporters that "a quick ceasefire remains crucial".

She added that Berlin "regretted" that talks with separatists had not been held and said they should take place as soon as possible.

Last week, the foreign ministers of Ukraine, Russia, Germany and France called for fresh ceasefire talks involving the OSCE, after the government in Kiev ended a 10-day truce with pro-Russian rebels amid renewed fighting.

On Sunday, resurgent Ukrainian forces pursued retreating separatists after seizing their symbolic bastion in Slavyansk in a morale-boosting win that appeared to dim hopes for a ceasefire in the deadly insurgency.