Along with the leaders of France, Germany and Italy, Romanian President Klaus Iohannis arrived in the Ukrainian capital city of Kyiv early on June 16.
"In Kyiv today with my European colleagues German Chancellor Olaf Scholz, French President Emmanuel Macron and Italian PM Mario Draghi Palazzo Chigi to show our strong support and full solidarity with Ukrainian President Zelensky and the Ukrainian people," Iohannis tweeted.
"This illegal Russian aggression must stop!"
Earlier Iohannis said that the EU candidate status must be granted to Ukraine as soon as possible.
"In my opinion, the candidate status must be granted as soon as possible, it is the correct solution from a moral, economic and security perspective," he said after talks with President Macron on June 15.
This is the first visit by any of the three leaders to Ukraine since the start of the full-scale Russian invasion.
The leaders visited the suburban town of Irpin to the north-west of Ukraine, which was severely damaged by Russian invasion forces during their failed attempt to capture the Ukrainian capital Kyiv in late February and March.