Russia troop reduction on Ukraine border welcomed
The Russian defence ministry said one motorised infantry battalion was withdrawing from the Rostov region.
After a meeting with his French and Polish counterparts, Mr Steinmeier said it was a "small signal" that the situation was becoming less tense.
Thousands of Russian soldiers are still said to be deployed along the border.
Earlier, Ukraine condemned a visit to Crimea by Russia's Prime Minister Dmitry Medvedev and a delegation of government ministers.
A note protesting against the presence of an official in "the territory of another state without preliminary agreement" had been sent, he added.
Crimeans voted to leave Ukraine for Russia on 16 March, in a poll condemned as illegal by the UN General Assembly.
Mr Medvedev announced that he would make Crimea a special economic zone. He also vowed to quickly boost salaries and pensions, and to improve education, healthcare and local infrastructure.
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