WASHINGTON — Defying Western efforts to confront the Islamic State (IS) on the battlefield, the group has evolved its reach and organisational ability, with increasingly dangerous hubs outside Iraq and Syria and strategies that call for using spectacular acts of violence against civilians.

But even as the militant attacks were playing out across Paris on Friday night, the United States carried out an airstrike — planned days in advance — against the leader of the IS in Libya, which has emerged as a pivotal stronghold for the group in North Africa. US and British Special Operations forces have for months been conducting secret surveillance missions in Libya to monitor the rise of fighters aligned with the IS.

The massacre in Paris on Friday, following bombings in Beirut and the downing of a Russian passenger jet over Egypt, all claimed by the IS, reveals a terrorist organisation that has changed in key ways from the West’s initial understanding of it as a group focused on holding territory in Syria and Iraq and building an Islamic state.

The IS has for the first time engaged in what appears to be a centrally planned campaign of terrorist attacks aimed at inflicting huge civilian casualties on distant territory, forcing many counter-terrorism officials in the US and Europe to recalibrate their assessment of the group.

“They have crossed some kind of Rubicon,” said Dr William McCants, a scholar at the Brookings Institution. “They have definitely shifted in their thinking.”

When the Sinai Province of the IS (an Egyptian offshoot) claimed responsibility for blowing up a Russian charter plane over Sinai two weeks ago, some analysts wondered if the group had acted on its own and leapt out in front, even at the cost of risking a Russian military backlash on the parent group in Syria and Iraq.

But the attacks last week in Paris and Beirut, which the IS also said it carried out, appear to have settled that question and convinced even sceptics that the central leadership was calling the shots.

“There is a radical change of perception by the terrorists that they can now act in Paris just as they act in Syria or Baghdad,” said Professor Mathieu Guidere, a terrorism specialist at the University of Toulouse. “With this action, a psychological barrier has been broken.”

At a time when many Western officials were most concerned about IS-inspired lone-wolf attacks, the ones in Paris have revived the spectre of coordinated, high-casualty attacks planned with the involvement of a relatively large number of perpetrators.

American and European authorities said the Paris assault bore the hallmarks of complex attacks conducted by Al Qaeda, or of the Mumbai plot in 2008.

The US broadened its fight against the Islamic State in Libya on Friday night, targeting and potentially killing the group’s senior leader, Abu Nabil, also known as Wissam Najm Abd Zayd Zubaydi, the Pentagon said Saturday. It marked the first time the US has targeted a senior IS operative outside Iraq or Syria. AGENCIES