The European Union will appeal an EU court decision ordering the removal of the Palestinian group Hamas from the EU terrorism blacklist, foreign policy chief Federica Mogherini said.

Mogherini said foreign ministers from the 28 member states decided at a meeting on Monday to appeal the decision taken by the General Court of the European Union on December 17.

"This ruling was clearly based on procedural grounds and did not imply any assessment by the court of the merits of designating the Hamas as a terrorist organisation," Mogherini said in a statement.

Last month's ruling by the EU's second highest court had said that the blacklisting of Hamas in 2001 was based not on sound legal judgments but on conclusions derived from the media and the internet.

Hamas was put on the EU terrorist list as part of broader measures to fight terrorism in the wake of the September 11 attacks and its funds were frozen.

Hamas, which has been in power in the Palestinian territory of Gaza since 2007, had appealed against its inclusion on the blacklist on several grounds.

Israel's closest ally the United States has urged the EU to keep up its sanctions on Hamas, saying the US position had "not changed" and Hamas is still a "designated foreign terrorist organisation".

Hamas slammed the EU appeal describing it as "immoral".

"The European Union's insistence on keeping Hamas on the list of terrorist organisations is an immoral step, and reflects the EU's total bias in favour of the Israeli occupation," Hamas spokesman, Sami Abu Zuhri, told AFP news agency.

"It provides it (Israel) with the cover for its crimes against the Palestinian people," he added.

The EU ministers were meeting in Brussels to discuss how to boost cooperation in the face of growing extremist threats following deadly Paris attacks and anti-terror raids in Belgium.