Boris Johnson and Irish Prime Minister Micheal Martin spoke of their “deep concern” at the “escalation of hostilities” near the Ukrainian capital Kyiv during a bilateral meeting in London.
The prime minister said it was a “critical moment” for Ukraine, as well as wider European and international security, when he joined the Taoiseach for talks on Saturday afternoon.
Earlier in the day, the Ministry of Defense (MoD) said fighting northwest of Kyiv was continuing, with the bulk of Russian ground forces about 25 kilometers from its center.
Meanwhile, the Ukrainian government said a mosque in the city of Mariupol had been shelled by the Russian army.
The mosque housed more than 80 people. There were no immediate reports of casualties.
Mr Johnson and Mr Martin spoke about the crisis in Ukraine and Northern Ireland protocol before watching Ireland beat England in the Six Nations at Twickenham.
A Downing Street spokesman said the two leaders spoke of their “deep concern at the escalation of hostilities near Kiev” and “condemned the attacks by Russian forces on civilians”.
“The prime minister said this is a critical moment for Ukraine and for wider European and international security,” the spokesperson added.
“They agreed on the vital importance of continued unity in the face of Russian aggression, including through humanitarian relief, defensive military support to the Ukrainian government and further sanctions targeting the Putin regime.”
Nice to meet the Prime Minister @BorisJohnson before the Ireland-England game.
We discussed the brutal invasion of #Ukraine by Russia and the ongoing humanitarian crisis.
We welcomed the close collaboration between the EU, the UK and our partners to hold Russia to account. pic.twitter.com/hDmzTfeIkL
— Michael Martin (@MichealMartinTD) March 12, 2022
Mr Johnson reportedly told Mr Martin he hoped the “same spirit of cooperation” that the UK and EU had shared during the Ukraine crisis could be applied to the protocol talks.
A spokesman for the Taoiseach’s office said the pair discussed “the brutal Russian invasion of Ukraine and the profound global security, economic and humanitarian consequences”.
They welcomed the “close collaboration” between the EU, UK and other partners to hold Russia to account and to meet the humanitarian needs of the Ukrainian people, the spokesman said.
The Ukraine crisis and protocol were expected to be high on the agenda at the leaders’ meeting this weekend.
The Irish Prime Minister is visiting the UK as part of a program of events to mark St Patrick’s Day.

Ahead of Saturday’s bilateral meeting, Mr Martin said he was not there to tell the Prime Minister what to do about the refugees.
Asked if he would encourage Mr Johnson and the UK Government to take in more people fleeing war in Ukraine, he told reporters at the Irish Embassy: ‘Well, to be fair, I am not here to tell Boris Johnson what to do.
“I have to acknowledge the leadership of the UK government in terms of the sanctions they imposed on Russia.
“And also the support he has given to Ukraine and even many Eastern European countries in the European Union who appreciate the support they have received from the UK and have said so.”

On Sunday, the Taoiseach will attend the St Patrick’s Day Festival and Parade in London, which this year will celebrate ‘community’ and key workers during the Covid-19 pandemic.