Greek Prime Minister Kyriakos Mitsotakis on Saturday called for the "swift resolution" of a probe into a crime journalist's shock murder, condemned by leading EU officials, political parties and unions.

"On (the PM's) express orders, the investigation will be expedited to the maximum degree," Citizen's Protection Minister Michalis Chrysohoidis told reporters after being summoned to an emergency meeting by Mitsotakis.

Giorgos Karaivaz, who worked for private TV station Star and ran the news blog, was shot several times Friday as he got out of his car outside his house in the southern Athens district of Alimos, witnesses said.

He had just returned home from work.

A police source told AFP the 52-year-old journalist had been shot by two men on a motorbike. Seventeen bullet casings were recovered from the scene.

The police minister called the murder "a heinous crime", adding that "the victim's status as a journalist gives the case particular importance."

The murder was rapidly condemned Friday by the European Commission and the Council of Europe commissioner for human rights.

"Murdering a journalist is a despicable, cowardly act," Commission chief Ursula von der Leyen tweeted Friday.

"Europe stands for freedom. And freedom of press may be the most sacred of all. Journalists must be able to work safely. My thoughts are with the family of George Karaivaz. I hope the criminals are soon brought to justice," she said.

Karaivaz had worked for some of Greece's leading newspapers and TV channels in a 32-year career.

The veteran crime reporter was shot dead outside his home
The veteran crime reporter was shot dead outside his home Eurokinissi / Yiannis PANAGOPOULOS

"(He) was one of the most experienced crime reporters in the field... and was held in high regard by colleagues," the Esiea union of Athens daily newspaper journalists said in a statement.

The federation of Greek police officers said Karaivaz was personally interested in improving working conditions for law enforcement and was "strongly critical of anybody" standing in their union's way.

While Greek media offices are frequently targeted in firebomb and vandalism attacks, journalist killings are rare.

Some journalists request police protection after receiving threats, but Karaivaz was unguarded.

"It was not his style to request protection," a police officer who knew Karaivaz well told AFP, speaking on condition of anonymity.

Karaivaz had recently been investigated by Greek justice over allegedly taking money from a reformed gangster who was murdered in 2019.

He had angrily denied any wrongdoing, and had written articles hinting at corruption within the police force on which he was scheduled to testify.

The shooting occurred at a time when Greek authorities had been criticised for allocating police guards to a controversial TV presenter.

In July, tabloid newspaper editor Stefanos Chios survived after being shot in the neck and chest by a hooded man outside his home.

The case is still under investigation.

In 2010, radio manager, blogger and investigative journalist Socratis Giolias was gunned down outside his home but the case was never solved.