A member of the Greek far-right group Golden Dawn has been killed in a drive-by shooting, ITV News sources have said.
Two other Golden Dawn members were reportedly critically injured in the attack, which took place outside the organisation's offices in Heraklion, Athens.
More top news
The suspect, 35-year-old Willie Corey Godbolt, has been arrested and was being treated for a gunshot wound in hospital.
Mohanna Abdhou, known as Montana, was out with friends when two attackers cycled up to them and opened fire in Brent, north-west London.
The US president tweeted that Mrs May gave him "full details" of the incident during talks while he attended summits in Europe.