The EU's leading states are to restart their rollout of the Oxford-AstraZeneca Covid-19 vaccine after Europe's medicines regulator concluded it was "safe and effective".

The European Medicines Agency (EMA) reviewed the jab after 13 European countries suspended use of the vaccine over fears of a link to blood clots.

It found the jab was "not associated" with a higher risk of clots.

Germany, France, Italy and Spain said they would resume using the jab.

It is up to individual EU states to decide whether and when to re-start vaccinations using the AstraZeneca vaccine. Sweden said it needed a "few days" to decide.

The World Health Organization (WHO) on Thursday called on countries to continue using the vaccine, and is due to release the results of its own review into the vaccine's safety on Friday.

The agency's investigation focused on a small number of cases of unusual blood disorders. In particular, it was looking at cases of cerebral venous thrombosis - blood clots in the head.

Decisions to suspend use of the vaccine sparked concerns over the pace of the region's vaccination drive, which had already been affected by supply shortages.

French Prime Minister Jean Castex announced new measures for his country on Thursday, saying the pandemic was clearly accelerating and a "third wave" of infections looked increasingly likely.

Mr Castex, 55, said he would receive the jab himself on Friday afternoon.

What did the EMA say exactly?

Emer Cooke, the agency's executive director, told a news conference: "This is a safe and effective vaccine."

"Its benefits in protecting people from Covid-19 with the associated risks of death and hospitalisation outweigh the possible risks."

The EMA's expert committee on medicine safety, Mrs Cooke said, had found that "the vaccine is not associated with an increase in the overall risk of... blood clots".

But the EMA, she added, could not rule out definitively a link between the vaccine and a "small number of cases of rare and unusual but very serious clotting disorders".

Therefore the committee has, she said, recommended raising awareness of these possible risks, making sure they are included in the product information. Additional investigations are being launched, Mrs Cooke added.

"If it was me, I would be vaccinated tomorrow," Mrs Cooke added. "But I would want to know that if anything happened to me after vaccination what I should do about it and that's what we're saying today."

Welcoming the review's endorsement of the vaccine as safe and effective, German Health Minister Jens Spahn added, "Doctors should be informed about the risk of venous thrombosis in women under 55 years of age, so that they in turn can inform patients."

Why did European countries act?

Thirteen European countries suspended use of the vaccine, after reports of a small number of cases of blood clots among vaccine recipients in the region.

Leading EU states said they had opted to pause their use of the drug as a "precautionary measure".

"There were a few very unusual and troubling cases which justify this pause and the analysis," French immunologist Alain Fischer, who heads a government advisory board, told France Inter radio. "It's not lost time."

In Germany, the health ministry also pointed to a small number of rare blood clots in vaccinated people when justifying its decision. It postponed a summit on extending the vaccine rollout ahead of the EMA's announcement.

Other countries, such as Austria, halted the use of certain batches of the drug, while Belgium, Poland and the Czech Republic were among those to say they would continue to administer the AstraZeneca vaccine.

Decisions to halt rollouts of the AstraZeneca vaccine were criticised by some politicians and scientists.

A spokeswoman for Germany's opposition Free Democrats said the decision had set back the country's entire vaccination rollout. German Greens health expert Janosch Dahmen, meanwhile, argued that authorities could have continued using the drug.

Dr Anthony Cox, who researches drug safety at the UK's University of Birmingham, told the BBC it was a "cascade of bad decision-making that's spread across Europe".

What has AstraZeneca said?

The company says there is no evidence of an increased risk of clotting due to the vaccine.

It said it had received 37 reports of blood clots out of more than 17 million people vaccinated in the EU and UK as of 8 March.

These figures were "much lower than would be expected to occur naturally in a general population of this size and is similar across other licensed Covid-19 vaccines", it said.

Professor Andrew Pollard, director of the Oxford vaccine group which developed the Oxford-AstraZeneca jab, told the BBC on Monday that there was "very reassuring evidence that there is no increase in a blood clot phenomenon here in the UK, where most of the doses in Europe [have] been given so far".

British Health Secretary Matt Hancock this week urged people to "listen to the regulators" and to "get the jab".