Washington, December 7

US President Barack Obama vowed yesterday that America would destroy the Islamic State group and hunt down its followers at home or abroad, in a rare address from the Oval Office to a jittery nation.

Facing questions about his leadership and strategy, Obama harnessed the highest trappings of US power to calm a country rattled by a rampage in California that killed 14 people.

“After so much war, many Americans are asking whether we are confronted by a cancer that has no immediate cure,” Obama said in a solemn speech, adding that the San Bernardino massacre was evidence of an “evolving” and increasingly homegrown threat.

As a father of two daughters, Obama said, he could imagine himself or his kin in San Bernardino or in Paris, where scores of people were killed last month in attacks claimed by Islamic State.

“Here’s what I want you to know,” he said. “The threat from terrorism is real, but we will overcome it. We will destroy ISIL and any other organisation that tries to harm us,” he said.

“Our military will continue to hunt down terrorist plotters in any country where it is necessary.”

Obama urged Muslims in America and around the world to “decisively and unequivocally reject the hateful ideology that groups like ISIL and al Qaeda promote.”

He detailed a multi-pronged strategy against the jihadists that will rely as much on community action, technology and countering propaganda as military force.

It is just the third time Obama has delivered an Oval Office address -- used by presidents since Harry Truman to convey resolve in the face of a national crisis.

A senior administration official said the speech was designed to convey the seriousness with which Obama was taking the shootings, which are being investigated as a terror attack.

On Wednesday, US-born Syed Farook and his Pakistani wife Tashfeen Malik dropped off their six-month-old daughter with her grandmother, donned tactical gear and burst into an office party full of Farook’s co-workers, spraying them with bullets.

Obama said the pair “had gone down the dark path of radicalisation.”

“They had stockpiled assault weapons, ammunition, and pipe bombs. So this was an act of terrorism.”

But he added that there was “no evidence that the killers were directed by a terrorist organisation overseas or that they were part of a broader conspiracy here at home.”

Both shooters died in a hail of police bullets, leaving questions about how, when and why they may have become radicalised.

The Islamic State has praised the attackers as “soldiers” of its self-proclaimed caliphate, while stopping short of claiming outright credit.

In an interview with Italian newspaper La Stampa, Farook’s father suggested his son approved of the group’s ideas and was fixated with Israel.

But several reports, citing unnamed officials, say investigators are looking into whether Malik radicalised her husband.