A former leading Ukrainian official has been shot dead outside an American school in the Spanish capital Madrid, authorities have confirmed.

Andriy Portnov, 51, had just dropped his children off at the school in the Pozuelo de Alarcón area of the city and was walking to his car in the school parking area.

At least one unidentified attacker fired several shots at the victim before fleeing into a wooded area in a nearby public park, witnesses said.

Portnov had been an MP and deputy head in the administration of Viktor Yanukovych, the pro-Russian president ousted in 2014 after months of protests.

He had previously been an MP in Yulia Tymoshenko's governing party, but switched to Yanukovych's team when he won the presidential election in 2010.

He left Ukraine after the revolution only to return in 2019 after Volodymyr Zelensky was elected president.

He then left Ukraine again, and in 2021 was sanctioned by the US Treasury, which said he had been "widely known as a court fixer" who had taken steps to control the judiciary and undermine reform efforts.

It was not clear who was behind the shooting that took place at about 09:15 local time (07:15 GMT) on Wednesday, reportedly as children were still entering the school.

Witnesses said there had been five or six shots. One student told Spanish TV he thought they were "firecrackers or fireworks". A woman who had rushed to Portnov's aid began to scream, according to El Mundo newspaper.

Police drones and a helicopter searched the area for a gunman who, according to witnesses, was a thin man in a blue tracksuit.

Spanish reports suggested the gunman may have had at least one accomplice riding on a motorbike. Hours after the shooting no arrests had been made.

A similar gun attack took place in 2018, when a Colombian drug trafficker was fatally shot outside a British Council school a few kilometres away.

But the motive behind Wednesday's attack is not yet known. Emergency services at the scene could only confirm that that Portnov had suffered several bullet wounds in the back and the head.

Portnov's black Mercedes car was cordoned off and the school wrote to parents to confirm that all the students inside were safe.

His body was later taken away for a post mortem examination.

Portnov had successfully challenged a series of lawsuits against him in recent years, both in Ukraine and abroad.

The European Union imposed sanctions on Portnov, but he challenged the move in court and won the case.

Ukraine's SBU security service had also opened a case for suspected treason over Russia's annexation of Crimea but that was dropped when it concluded no offence had been committed.

Although Ukraine's intelligence services have been linked to several killings in Russia and occupied areas of Ukraine, a fatal attack in Spain in February last year was linked to Russian hitmen.

The victim, a Russian helicopter pilot, was shot dead near Alicante, months after defecting to Ukraine.

Authorities in Kyiv said they had offered to protect Maxim Kuzminov in Ukraine, but he is believed to have moved to Spain's south-east coast under a false identity.