European Union member states agreed at a summit in Brussels to take further punitive steps against Russia in the coming days for the nerve agent attack in Salisbury, as Moscow accused the bloc of joining a London-driven hate campaign against it.

Late on Thursday, in a boost for British Prime Minister Theresa May, the 28-member EU collectively condemned the attack on a former Russian spy and said it was "highly likely" Moscow was responsible. They also recalled the EU ambassador to Russia.

"Additional steps are expected as early as Monday at the national level," summit chair Donald Tusk told reporters.

French President Emmanuel Macron said Paris and Berlin would be among countries taking further rapid and coordinated measures which other leaders said would include the expulsion of Russian officials and possible other retaliatory actions.

"We consider this attack a serious challenge to our security and European sovereignty so it calls for a coordinated and determined response from the European Union and its member states," Macron told a news conference.

Standing beside him, German Chancellor Angela Merkel said EU countries would debate what measures to take "and then act".

One senior official familiar with discussions said the extent of measures in the coming weeks could be "surprising" and not confined to expulsions. There is no talk of more economic sanctions, whose enforcement has divided the EU in the past.