The European Union is prepared to take further action against Russia if tensions with Ukraine escalate, leaders from three EU countries told CNBC following Thursday's EU summit in Brussels.

Fredrik Reinfeldt, the Prime Minister of Sweden, told CNBC, said while Russia has played down the impact of the sanctions, the country's economy was likely to be impacted. "I don't think we should listen so much to the way [Russian President Vladimir] Putin is trying to behave when it comes to this," said Reinfeldt. (Read more: Ukraine: What next for battered economy?)

"[It's] very foreseeable that they say that they don't care about anything, but we have in history seen that these targeted measures are probably better working sanctions than many other things that you could do," he added.

Russian armed forces stand guard around the Ukrainian military base in the village of Perevalne, 20 km south of Simferopol. Bulent Doruk | Anadolu Agency| Getty Images

EU leaders agreed on Thursday to expand the bloc's list of people targeted with sanctions over tensions in Ukraine by 12 names, and asked the European Commission to prepare an assessment of the potential impact of broad economic sanctions against Russia.

The EU has already placed sanctions on 21 people, but media reports have said Russian leaders have apparently dismissed their impact. (Read more: Fund managers take risk off the table amid Ukraine crisis)

It was reported by Russian news agency Itar-Tass that Russian Foreign Affairs Committee Deputy Chairman Alexander Romanovich called the U.S. and EU sanctions "absurd and unreal" on Thursday. "Basically Russia is hurting itself, it's hurting their economy. Investors will leave, they're making their neighbors nervous and they will lose political influence. So this is not the equation for long term stability and a strong Russia," said Reinfeldt, who added that the 12 names to be added to the list were more closely linked to the Russia's invasion of Crimea. Meanwhile, U.K. Prime Minister David Cameron also told CNBC Asia the EU leaders were in agreement over the need for Russia to be sent a strong message that any further escalation of the conflict would have consequences. (Read more: )