Moscow, Russia: Russia on Thursday pledged broad retaliatory measures against Turkey’s economy in revenge for the downing of one of its warplane, as recriminations between Moscow and Ankara reached fever pitch.

President Vladimir Putin demanded an apology but his Turkish counterpart Recep Tayyip Erdogan bluntly refused, accusing Moscow of slander over claims his country was supporting the brutal Islamic State group.

The downing of the plane raised fears it could fuel a wider geopolitical conflict and highlighted the difficulty of forging consensus on the fate of Syria as French President Francois Hollande arrived in Moscow for talks with Putin.

While Russia ruled out any military retaliation against NATO member Turkey over Tuesday’s incident, Prime Minister Dmitry Medvedev gave his ministers two days to work out “a system of response measures” in the economic and humanitarian spheres.

He said the broad punitive steps for what he termed “this act of aggression” could include halting joint economic projects, restricting financial and trade transactions and changing customs duties.

Measures could also target transport and tourism after Putin told citizens not to travel to Turkey, a hugely popular tourist destination.

The foreign ministry also urged those already in the country Turkey to return home due to “existing terrorist threats”.

Russia also tightened control over Turkish food imports over alleged safety standard violations, saying it would organise additional checks at the border and production sites in Turkey.

Economy minister Alexei Ulyukayev for his part did not rule out that the measures could hit two major projects with Turkey—the planned Turk Stream gas pipeline and the Akkuyu nuclear power plant—in a move that looked set to rattle cages in energy-poor Turkey.

In another move likely to infuriate Ankara, lawmakers from the Kremlin-friendly A Just Russia party introduced a bill calling for a maximum punishment of five years in jail for those who deny the mass killing of Armenians by Ottoman Turkey in 1915 was a genocide.

Turkey has always denied the killings were a premeditated attempt by the Ottoman Empire to wipe out the Armenians.

‘Shame on you’

Ahead of the Hollande talks on the Syrian crisis, Putin and Erdogan traded barbs, with the Kremlin chief saying he was waiting for an apology and Erdogan ruling out any such move.

“We are under the impression that the Turkish leadership is deliberately pushing Russian-Turkish relations into deadlock. We regret that,” said Putin.

He flayed Turkey for “treacherous stabs in the back” and accused its leadership of buttressing the IS jihadists financially and militarily.

Erdogan insisted his country did not buy any oil from the Islamic State group.

“Shame on you. Those who claim we buy oil from Daesh are obliged to prove it. If not, you are a slanderer,” he said in a speech.

He also refused to make amends, saying it was Russia that needed to apologise.

“I think if there is a party that needs to apologise, it is not us,” he told CNN separately.

Analysts said that while both countries can ill-afford a permanent rupture in ties, the clash of egos between the two leaders could further damage relations.

“Their desire not to lose face has the potential to weaken otherwise pragmatic calculations to contain the crisis,” said Anthony Skinner, director of political risk at Verisk Maplecroft.

Moscow targets rebels

The shooting down of the aircraft by Turkey is thought to be the first downing of a Russian plane by a NATO member since 1952 when US pilots shot down a Soviet plane near Vladivostok during the Korean War.

It led to the death of one of two pilots and a soldier who took part in a failed rescue operation—Moscow’s first combat losses since the start of its Syria campaign.

On Thursday, Moscow said its forces had wiped out Syrian rebel groups operating in the area where its jet was brought down, unleashing a huge bombardment after rescuing a pilot. 

Turkey insists its forces repeatedly warned the Russian aircraft, an assertion backed up by the United States.

Some observers believe Ankara shot down the jet out of anger over Moscow’s strikes against ethnic Turkmen in Syria, a minority it views as an ally in its struggle against Bashar al-Assad’s regime.

Moscow claims the plane never crossed over the border from Syria, and Russian Foreign Minister Sergei Lavrov has branded the incident a “planned provocation.”

The raging tensions have threatened to derail Hollande’s marathon effort to try to cobble together a broad anti-IS coalition that would include global and regional players.

After jihadists killed 130 people in Paris this month in attacks claimed by the IS group, the French leader held talks with US President Barack Obama and German Chancellor Angela Merkel.

Few expect the Kremlin talks to produce a breakthrough, however.