Zelensky rallies EU support as Trump says Ukraine leader 'more difficult to deal with than Putin'

US President Donald Trump has renewed his sharp criticism of Volodymyr Zelensky, saying the Ukrainian leader is "more difficult to deal with than [Russian President Vladimir] Putin".

Speaking to US media on Thursday evening, Trump also called Ukraine's fresh wave of strikes on Russian oil refineries a "disgrace".

Zelensky, who is in Brussels for a summit with EU leaders, had paused the attacks for three days at Trump's request for a ceasefire on energy targets, but said on Thursday the strikes would resume because Moscow had never stopped.

Meanwhile, deadly attacks on Ukraine continued overnight, with several people killed in a Russian drone strike in the north-eastern city of Kharkiv, the regional governor said.

At least 14 people were injured, Oleg Synegubov wrote on Telegram.

Zelensky has not commented on Trump's latest criticism. He arrived at the summit in Brussels flanked by European Commission President Ursula von der Leyen and European Council President António Costa.

"Of course we supported President Trump's energy ceasefire but we've seen that Russia did not respect it, not a single minute," Von der Leyen told reporters. "Russia escalated and therefore we have to increase sanctions on Russia... We will not lift any sanctions unless Russia stops the war."