Steinmeier, speaking in Kyiv after talks with Ukrainian Prime Minister Arseniy Yatsenyuk, called for the release of all hostages in eastern Ukraine and for separatists to vacate seized government buildings.
He said the situation in certain parts of Ukraine remains "dangerous and threatening."
Steinmeier also met with acting Foreign Minister Andriy Deshchytsya and acting President President Oleksandr Turchynov before flying to Odesa.
But Yatsenyuk said the key to resolving the destabilizing situation in Ukraine "is not in Kyiv but in Moscow."
Yatsenyuk also thanked German diplomat Wolfgang Ischinger, organizer of Munich's annual security conference, for offering to moderate any round-table talks.
Kiev-appointed governor Serhiy Taruta meets the press in Donetsk today. Vows May 25 election will happen: pic.twitter.com/sJbqQdfKij
— Mark MacKinnon (@markmackinnon) May 13, 2014
RT @shaunwalker7 Donetsk people's republic has banned Obama, Merkel, Ashton from entrance. pic.twitter.com/MhNv6b3Xow (via @dnrpress)
— Mark MacKinnon (@markmackinnon) May 13, 2014
He said if evidence of such activities is found, a court should ban the party.
Turchynov told parliament today that "there is a lot of information and material on the complicity" of Communist Party members in separatist activities.
He also accused Communist Party leader Petro Symonenko of spreading "lies" and pro-Russian "propaganda" about events in the southern city of Mariupol, where at least seven people were killed in clashes between security forces and armed pro-Russian separatists on May 9.
Symonenko earlier told parliament that during a May 9 raid on police headquarters in Mariupol, special forces killed police officers who refused to use weapons to disperse protesters.
Turchynov called this "lies and incorrect information."
Gazprom officially informs #Ukraine that it will introduce prepayment for gas supplies starting from June http://t.co/64qSH113TV
— Paul Sonne (@PaulSonne) May 13, 2014
Just left rebel base in Slovyansk. Everyone was watching a Russian TV retread of an old anti-Nazi movie. Russian TV keeps this pump primed.
— C.J. Chivers (@cjchivers) May 13, 2014
Read more here
#Russia economy minister repeats earlier warnings that country to be in recession by the time 2nd quarter ends @Reuters
— Thomas Grove (@tggrove) May 13, 2014
@cjchivers with @nytimes writes Ukrainian forces shelling Slavyansk with 120-millimeter rounds http://t.co/uve8LbEZKq UKR sources deny it.
— Ryskeldi Satke (@RyskeldiSatke) May 13, 2014
Single mother Olga is afraid of the #Donetsk separatists & wants a united #Ukraine. Watch more http://t.co/LCklX5N3m8 pic.twitter.com/OzGybWrxl5
— Will Vernon (@BBCWillVernon) May 13, 2014