"The aggressor must be treated as an aggressor. And such a brutal aggressor must be treated accordingly. So, sanctions must be tightened and we have agreed on that", the Lithuanian president said in a video comment on Friday night after a European Council meeting in Brussels.
"Yes, we have to admit that some countries are not yet ready to disconnect from the Russian energy taps in the very near future," he added.
In his words, European leaders discussed what can be done about both coal and oil imports.
"We can only be glad that Lithuania has done a lot here and could be a role model for other countries," the president said.
He suggests including into the EU's 5th package extensive sanctions on Russia's energy and transport sectors, blocking Russian and Belarusian banks not yet on the sanctions list, and banning Russian ships from EU ports.
The importance of sanctions was also stressed by Ukrainian President Volodymyr Zelensky when he addressed EU leaders on Thursday, Nauseda said.
"President Zelensky appealed for our unity, he appealed from the Ukrainian side. The fact that we support and back him wholeheartedly, his wish is that this should be reflected in our decisions, that those decisions should be decisive and help Ukraine not tomorrow, not the day after tomorrow, but today," Nauseda said.
"First of all, it's military aid (...) He also talked about sanctions, about the fact that sanctions against Russia are necessary simply because the resources we are acquiring are becoming a resource to finance the war, which is unacceptable, and people are dying as a result of it", he added.
UN data shows that more than 3.6 million refugees have fled Ukraine in the space of one month since the war started, with more than 970 civilian casualties reported.
At the same time, Russia has been hit by a raft of international sanctions that have crippled its economy.