BEIRUT: By bombing a Russian passenger plane over Egypt and carrying out deadly attacks in Paris, the self-styled Islamic State (IS) group has demonstrated both its resilience and its growing international reach, experts say.

Unlike its forerunner and now rival Al-Qaeda, which has focused largely on spectacular foreign attacks, IS has promoted a strategy of “remaining and expanding” in territory in Syria and Iraq.

But with the Paris and Egypt attacks, it has shown it can also rely on affiliates and sympathisers to strike abroad, even as its “caliphate” is attacked by a US-led coalition, Russian air strikes, Iraqi and Syrian government troops and Kurdish forces.

“I think it's a logical step in the progression of Islamic State strategy,“ said IS expert and researcher Charlie Winter of the international attacks.

In the 18 months since its leader declared a “caliphate” in Syria and Iraq, IS has attracted pledges of allegiance from a series of international affiliates, including the Egyptian group that claimed responsibility for downing a Russian plane over Sinai on October 31.

The group did not disclose how it brought the plane down, creating initial doubts about whether the crash that killed 224 people was an attack.

But on Tuesday, Russia's security chief Alexander Bortnikov said Moscow had determined “unequivocally that this was a terrorist attack”.

In response, Russia's President Vladimir Putin pledged to “find and punish” the attackers, and to step up the air campaign Moscow began in Syria in late September.

'Well-prepared, coordinated'

Winter said the French attacks in particular, which involved multiple simultaneous assaults and killed at least 129 people, demonstrated careful planning.

“The sophistication of the attack shows that it was well-prepared and coordinated and it follows training,” he said.

But Romain Caillet, an expert on militant groups, said they represented less an evolution of IS strategy than fulfilment of a longstanding goal.

“Each time IS has had the opportunity to hit an international target, it has done so,” he told AFP.

In Egypt, the group's affiliate had already claimed a bomb that hit the Italian consulate in Cairo in July, as well as the beheading of a Croatian kidnapped in Cairo, and the killing of an American working for an oil company.

Mokhtar Awad, an analyst at the Centre for American Progress, said the nature and scale of the Egypt attacks marked a “clear departure” for the IS affiliate.

He suggested they had been ordered or directed by IS's leadership outside of Egypt.

“I personally lean to thinking at the moment that it may have likely come from IS central because it advances their interests far more clearly than it does the local affiliate," he said.

'Do they communicate?'

Other experts are more sceptical that foreign sympathisers and affiliates rely on direct orders from the group's top leadership.

They point to numerous disrupted IS plots as evidence of the group's policy to hit foreign targets and say it is unlikely that affiliates or sympathisers wait for direct orders.

“How they communicate about very sensitive information, do they communicate? There is a debate among specialists,” said Caillet.

“No one actually knows the scale of communication between IS's leadership and its affiliates and sympathisers abroad", added Winter.

The attacks could also represent a shift in the dynamics of the foreign fighter flow to IS, said Clint Watts, a senior fellow at the Foreign Policy Research Institute.

“Over the past year, many foreign fighters have begun leaving Syria and Iraq and returning home, that leaves many well-trained and experienced fighters to plot attacks,” he told AFP.

“Second, it's become more difficult to get to Iraq and Syria, thus those supporters that want to join can't get to the fight in Syria, and they may act out at home.“

Experts estimate upwards of 25,000 foreign fighters have joined terrorist groups in Iraq and Syria, including some 4,500 Westerners.

Western intelligence agencies have long warned of the risk that well-trained returnees from the conflicts in Syria and Iraq could conduct attacks at home.