EU commissioner Ylva Johansson said Friday that migrant pushbacks were illegal, speaking before a conference in Lithuania, where authorities have been criticised for the practice by human rights groups.

"Pushbacks are clearly illegal. People have the right to apply for asylum," said Johansson, the EU's home affairs commissioner.

Thousands of migrants - mainly from the Middle East - have crossed or tried to cross the eastern border of the European Union into Latvia, Lithuania or Poland since last summer.

In Lithuania alone, almost 8,200 people have been denied entry in what aid groups describe as illegal pushbacks.

Governments in the region have defended the tactic, saying it is the only way to stop the influx, which the West blames on the Belarusian regime.

"We must not stick to bureaucracy. We must act, especially when we are attacked," Polish Interior Minister Mariusz Kaminski said after the conference on migration in Vilnius.

Lithuanian Interior Minister Agne Bilotaite said the country will further "defend itself and the European Union's external border" despite the criticism, but called for the bloc to find common ground on migration.

"To protect ourselves effectively, we need to develop a new standard for border protection," the minister said.

"We look forward to the constructive debate on the legislative proposal put forward by the European Commission," she added.

Fabrice Leggeri, head of the EU border agency Frontex, also said he wanted "legal clarification" on border management in order to know "what is possible and what is not".

Eastern members of the European Union have also sought funding from the bloc to finance fences they are building along their borders with Belarus.

Greek Migration Minister Notis Mitarachi also said he was in favour, telling reporters that border fences "must be eligible for funding from the European Union".

But Johansson said she was against it.

"If member states would like to build fences they can do so, but it is a longstanding position from the Commission not to finance walls or barbed-wire fences," she said.

Ministers from 14 EU member states visited Lithuania's snowy border with Belarus on Friday before the conference on the issue in the capital Vilnius.

Attempted illegal crossings have dropped significantly in recent weeks but Lithuania's interior minister said the calm at the border was "deceptive".

"Our border guards know that a group of migrants being forcibly pushed by Belarusian officials could appear there at any moment," she said.