EU leaders resolved to keep the bloc's internal borders open on Thursday evening but said new restrictions such as pre-departure Covid-19 tests are needed to keep fast-spreading new coronavirus variants in check.

"Across Europe, the health situation remains very serious. There is reason for hope because of the vaccines, but there's also strong reason for concern with the new variants," European Commission President, Ursula von der Leyen said after a video summit.

The EU should designate "dark red zones" - adding a new risk category to the existing scale - for areas where the new coronavirus is very prevalent, the top EU official said.

Travellers from these areas could be obliged to produce negative tests before arrival or to take on additional quarantine requirements, von der Leyen said, after the 27 EU leaders wrapped up their talks.

All non-essential travel - within the EU and for those wishing to enter the bloc - should be strongly discouraged, she told reporters in Brussels at a press conference alongside European Council President Charles Michel.

Belgium and Germany were among those pushing for stricter controls ahead of Thursday's talks.

When Covid-19 first hit Europe early last year, some EU states snapped their frontiers shut overnight.

This caused chaos for freight and passenger transport in the bloc, where economic well-being is highly dependent on the flow of goods and workers.

To avoid a repeat response, the EU heads of state and government must convince each other that they are doing enough to stop the new virus mutations - seen in Britain, South Africa and Brazil - from taking hold in Europe.

EU governments are under great pressure to step up the pace of inoculation.

The leaders welcomed a goal suggested by the commission to vaccinate 70 per cent of the EU population by summer, according to von der Leyen - but did not commit to a binding target on Thursday.

Increasing the rate of genomic sequencing - which helps track the emergence and spread of new mutations - is also key, she added.

At present, almost all states are sequencing less than 1 per cent of positive coronavirus tests. This needs to increase to 5 per cent, von der Leyen urged.

The EU health agency on Thursday similarly advised against non-essential travel and supported enhanced testing as part of the measures to slow down the importation and spread new variants.

"The risk associated with the introduction and community spread of variants of concern has been increased to high/very high," the European Centre for Disease Prevention and Control (ECDC) said.

National governments should ready their health services for greater pressure and speed up vaccination of high-risk groups, the Stockholm-based body warned.

The ECDC had earlier called for countries to carry out genome sequencing to help track the variants.

Several states dependent on tourism, including Greece and Spain, are meanwhile to introduce a European "vaccine passport," which would allow restrictions to be lifted for those who have received a jab.

Israel is setting up a similar domestic scheme. All Israelis who have been inoculated will be able to apply for a "green pass," allowing them to board flights with no need to quarantine on arrival.

Such privileges for the vaccinated are controversial, chiefly due to a lack of data on post-inoculation transmission.

While EU leaders agreed it was important to recognize each other's vaccination certificates, von der Leyen said, it is too soon to decide whether these could also entitle holders to extra perks like travel.

"Later on, when the time is right, we will need a thorough debate," the German politician said, pointing to unanswered medical questions about transmission and the length of vaccines' effectiveness.

EU governments did agree, however, on a framework for the mutual recognition of each other's tests - both rapid antigen testing and PCR probes.