Josep Borrell Fontelles states on Twitter that he had a telephone conversation with Ukrainian Foreign Minister Dmytro Kuleba.
The statement was made Sunday night.
He writes that the EU gives its relentless support for Ukraine's sovereignty and territorial integrity.
Borrell Fontelles, the EU foreign policy chief, added that the talks took place due to serious concerns about Russian military activity near Ukraine.
The statement is almost identical to the statement made by the White House on Good Friday, and on Monday afternoon the United States and Russia are in contact at the highest level, reports Reuters.
Troop reinforcements at the border
Ukraine recently accused Russia of reinforcing with thousands of troops near Ukraine's northern and eastern borders, as well as the illegally annexed Crimean peninsula by Russia.
The Kremlin's spokesman, Dmitry Peskov, said on Monday that Russia was making the necessary troop movements in its own country and that they were not threatening anyone.
The Russian government has previously said that any deployment of NATO troops in Ukraine will lead to further tensions and force Moscow to take action for its own security.
Ukraine announced over the Easter weekend that it will conduct military exercises this summer with five NATO countries.
The announced exercises include about 1,000 soldiers, according to Ukraine's Defense Headquarters.
Top diplomats
EU Foreign Minister Josep Borrell Fontelles has said he will continue talks with Kiev's top diplomats and foreign ministers in the EU's 27 member states.
They will have a meeting "later this month", reports The Guardian.