Prime Minister Boris Johnson has held talks in Kyiv with Ukraine's President Volodymyr Zelensky, Downing Street has said according to the BBC.
The website No 10 said the visit was "show of solidarity" with the Ukrainian people.
A spokesman said Mr Johnson was using the trip to set out a new package of financial and military aid.
It comes the day after the UK announced £100m of weapons for Ukraine after the bombing of refugees at a railway station.
The spokesman said, "The prime minister has traveled to Ukraine to meet President Zelensky in person, in a show of solidarity with the Ukrainian people," he said.
"They will discuss the UK's long-term support to Ukraine and the PM will set out a new package of financial and military aid."
The prime minister said the UK will send additional military equipment including Starstreak anti-aircraft missiles and 800 anti-tank missiles.
The western countries first pushed Ukraine into offering NATO membership which provoked Russia to start a military campaign in the eastern European country with the aim of demilitarizing it. Then the West rushed to help Ukraine to repel the Russian attack. No end is in sight for the conflict in Ukraine any time soon.
KI