EU lawmakers on Thursday reached a long delayed deal on tougher rules to curb terror content online, including an obligation that platforms take down offending material within an hour.

The regulation, which will need final approval by European Parliament and EU ministers, will also give national authorities the power to order content removals in other member states.

"Today's agreement is an important milestone in helping to prevent future attacks," EU vice-president Margaritis Schinas said, after EU member states and the European Parliament finalised the proposed regulation.

French Europe Minister Clement Beaune hailed the compromise, calling it "a major step forward, led by France", though the details of the accord were not yet available.

EU Commissioner for Home Affairs Ylva Johansson said the accord would guarantee that "what is illegal offline is illegal online".

The plan was launched in 2018 after a series of deadly terror attacks in France, Belgium and other EU countries, perpetrated by Islamic State inspired attackers, many indoctrinated through the internet.

However, concern that the measures would infringe free speech slowed the adoption of the regulation.

To address these concerns, a complaint mechanism for individuals is included in the proposal, the EU commission said.

Sources said governments will also have the power to object to a takedown order from a partner country in a complaint that would have to be scrutinised within 72 hours.

The rules became an even higher priority after last year's Christchurch mosques attack in New Zealand, which was broadcast live on Facebook.

The killing in October by a young Chechen of Samuel Paty, a French teacher who showed children in his class caricatures of Mohamed, increased the urgency to draw up legislation.

"Terrorist propaganda has played a key role in recent attacks in Europe. The difference between a video being on line for an hour, three hours, 24 hours millions of views," said Javier Zarzalejos, a conservative Spanish European lawmaker.

Centrist Spanish lawmaker Maite Pagazaurtundua said the agreement would safeguard freedom of expression while providing for the removal of illegal content.

However, NGO Liberties expressed disquiet in finding the move represented "a threat to fundamental rights".

The accord is designed to permit material of an educational, journalistic or artistic nature or facilitating research designed to raise awareness of the danger terrorism poses.

Liberties' Eva Simon welcomed that but said it was not sufficient entirely to ward off the NGO's concern that some governments might seek to use a vague definition of terrorist content to censor material and limit criticism of its own activities.