Greece has indefinitely suspended its top soccer league, a day after the owner of PAOK Thessaloniki marched onto the field carrying a gun following a disputed goal in a match.
FIFA urged Greek authorities to take swift action against PAOK owner Ivan Savvidis or face a possible suspension.
Savvidis walked onto the field twice accompanied by bodyguards, and appeared to be carrying a pistol in a holster around his waist.
He made no move to use the weapon at any time.
Fernando Varela had just scored in the 90th minute on Sunday for PAOK against AEK Athens, putting the hosts ahead 1-0 in the northern city of Thessaloniki.
The referee signalled a goal but then seemed to disallow it for offside. The match was eventually abandoned.
"The FIFA monitoring committee … strongly condemns the recent incidents in Greece and urges all national football stakeholders to act immediately to put an end to the unacceptable situation arising in Greek football," a FIFA statement said.
Giorgos Vasileiadis, Greece's Deputy Minister for Sport, met with Greece's Prime Minister and said league play was suspended, adding it would not restart "if there is not a new, clear framework agreed to by all so we can move forward with conditions and regulations".
'Greek press exaggerate the facts'
Greece has faced an unusually volatile league championship this season, with traditionally dominant Olympiakos — which has failed to win the title only twice in the past 21 years — in third place, behind leader AEK and PAOK.
Police said earlier on Monday they were investigating Savvidis, who holds a gun licence, for illegal entry onto the field and for possession of an object that could cause harm in a sporting venue.
Tatyana Gordina, the deputy CEO in charge of corporate communications at Savvidis' Russia-based Agrocom Group, stressed Savvidis had not made any threatening gestures.
"There were no threats made by Ivan Savvidis, especially not involving the use of a weapon, during yesterday's match," she said.
"There was an emotional walk out onto the field, probably a breach of sporting regulations, and nothing more.
"Most of the headlines in the Greek press exaggerate the facts."
Vasileiadis said Greek sporting authorities were "in open contact with UEFA" and would be holding meetings with the Greek soccer federation later on Monday to discuss further moves.
"The Government for the past three years has given great battles to manage to clean up the troubled football sector," the Minister said.
"We have won a lot, but much more remains to be done.
"In any case, we will not allow all this effort to be endangered, we will not allow phenomena of the past to be resurrected."
Savvidis, who took over PAOK in 2012, is a Russian-Greek businessman born in Georgia during the Soviet era who made his money with the privatisation of a cigarette factory in southern Russia in the 1990s.
His Agrocom company has extensive interests in tobacco, agriculture and real estate.
He spent two terms in Russian parliament from 2003-11.