German Foreign Minister Annalena Baerbock is in Ukraine's martyred town of Bucha, north of Kyiv, as part of a surprise visit to Ukraine.

Russian troops are accused of massacring hundreds of civilians as they retreated from Bucha and other Kyiv suburbs in late March.

Images of corpses lying in the streets, some with their hands bound, shocked the world and prompted calls for war crimes charges to be brought against Russia.