(Adds planned talk with Mogherini, details, background)
ASTANA, Nov 10 (Reuters) - German Foreign Minister Frank-Walter Steinmeier said on Monday the situation in Ukraine's rebel-held eastern regions had again become serious and all sides must respect a ceasefire agreement.
His comments during a visit to Kazakhstan underlined growing concern about an increase in fighting between pro-Russian separatists and government forces in the past week despite a ceasefire agreed in the Belarussian capital, Minsk, on Sept. 5.
"Unfortunately, the situation is again serious. I now think that we must call upon all those involved in this conflict, as well as the Russian side, to return again to the terms of the Minsk protocol," Steinmeier told a news conference.
East Ukraine's rebel stronghold Donetsk was pummelled on Sunday by the heaviest shelling in a month, and the Organization for Security and Cooperation in Europe said it had spotted an armoured column of troops without insignia in rebel territory that Kiev said proved Moscow had sent reinforcements.
Each side accuses the other of violating the terms of the peace plan. Russia denies being a party to the conflict and says it has not sent troops or weapons to east Ukraine.
Steinmeier said that on his return to Berlin on Monday evening he would discuss the situation in Ukraine with the European Union's foreign policy chief, Federica Mogherini. (Reporting by Raushan Nurshayeva; Writing by Dmitry Solovyov, editing by Timothy Heritage)
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