European Commission President Ursula von der Leyen set off for the Ukrainian capital Kiev early Friday morning, where she will meet President Volodymyr Zelensky.
She was accompanied by EU foreign affairs chief Josep Borrell.
Von der Leyen - a former German defence minister - set off from the small southern Polish town of Przemysl, just 13 kilometres from the Ukrainian border. The airspace over Ukraine is closed because of the war.
Von der Leyen will be the first Western leader to visit Ukraine since the atrocities in the Kiev suburb of Bucha were exposed in recent days.
In mid-March the prime ministers of Poland, Slovenia and the Czech Republic travelled to Kiev by train. Last week, European Parliament President Roberta Metsola visited the city.
In response to the murder of hundreds of civilians in Bucha, von der Leyen proposed a fifth sanctions package targeting Russia on Tuesday.
Sanctions on coal, wood, vodka
Representatives of the 27 EU states gave their backing to this late Thursday, including an import ban on coal, wood and vodka.
Top EU officials said a total fossil fuel import ban could eventually follow if Russia keeps up its war against Ukraine.
In order for the new sanctions to enter into force, they must be published in the Official Journal of the EU. This step is considered a formality and is expected to be completed on Friday.
Sources said there had been disagreement among EU members over whether the coal embargo should take effect in three or four months. Ultimately, at the request of countries including Germany, the member states decided on four.