The President of the European Council has condemned a decision by Belarus to allow illegal migrants to cross into the EU.
Charles Michel said that the EU "speaks with one voice" against Belarus during a press conference in Vilnius on Monday.
Lithuania has declared a state of emergency due to the massive flow of migrants arriving from neighbouring Belarus, mainly Afghans and Iraqis.
An estimated 150 people were arriving in the country each day, more than had entered annually in any of the last three years.
Belarusian President Alexander Lukashenko had said in May that his country would no longer prevent refugees from crossing its western border into Lithuania, in response to EU sanctions.
"Lithuanian borders are European borders," Michel tweeted on Monday.
"The EU implemented sanctions against Belarus and keeps fighting to promote our values. You can count on the EU to bring more support to Lithuania and its people."
Michel visited the Lithuania border in Padvarionys on Tuesday after a summit with the country's president, Gitanas Nauseda.
"We condemn all attempts to instrumentalise illegal migration to exert pressure on EU member states," Michel added on Twitter.
"Lithuania can count on our full support and solidarity through the mobilisation of Frontex, and dialogue with countries involved in return and readmission procedures."
During his visit to Vilnius, The European Council president will also meet Belarusian opposition leader Sviatlana Tsikhanousaya.
Michel said he will be speaking with Iraq's president next week to discuss the repatriation of Iraqi nationals.