The physical explosions of the U.S.-British airstrikes were felt and heard in the cities of Afghanistan, but the political reverbations of the first attack in the war on terrorism rattled capitals across the world.
"We are supported by the collective will of the world," President George W. Bush said in a televised speech from the Treaty Room in his White House residence. "Every nation has a choice to make."
"In this conflict, there is no neutral ground," Bush said. "If any government sponsors the outlaws and killers of innocents, they have become outlaws and murderers themselves. And they will take that lonely path at their own peril."
The Taliban, which rule Afghanistan, said it was ready for a holy war and vowed to fight "to the last breath."
A senior spokesman for Hamas, the militant Palestinian group, cast the U.S. as the villain in the Sunday attacks.
"What America has done is pure terrorism against an innocent people when there was no proof they were involved in the Sept. 11 attacks" Hassan Youssef told Reuters.
Iran, no friend to either the U.S. or the Taliban, called the assault "unacceptable," BBC reported.
Most of the initial responses were supportive of the actions taken by Washington and London. British Prime Minister Tony Blair said the military strikes did not weaken but actually strengthened the coalition in what Bush called a "war against terrorism."
"The world understands the danger in acting, but the danger of inaction is far greater," he said.
In Britain, which Bush called America's "best friend" and "staunchest" ally, the support came in the form of missiles fired from two British submarines in coordination with the U.S. attacks.
"The attacks represented the worst terrorist act against our citizens, but even if no British citizen had died, it would be right to act," Blair said in an address to his countrymen. "This atrocity was an attack on us all."
French President Jacques Chirac said French forces were poised to enter the fray alongside American and British soldiers, sailors and airmen.
Blair and Bush said Australia, Canada and Germany will also take part in the military strikes.
Russian President Vladimir Putin fully backed the anti-terrorism attacks, with a Foreign Ministry spokesman reading a statement on Russian television that Afghanistan had become an "international center of terrorism and extremism."
"It is time for decisive action with this evil," he said. "Terrorists wherever they are — in Afghanistan, Chechnya, the Middle East, or the Balkans — should know that they will be taken to justice."
German Chancellor Gerhard Schroeder was among the first to offer his support, pledging Germany's "unreserved" backing against what he called "terrorist targets" and stressing his country's "unlimited solidarity" with the United States.
At least as important was the encouraging statements coming from Pakistani President Pervez Musharraf.
"The president is part of the international effort to combat terrorism and fully supports the action taken today," a spokesman for Musharraf said.
Pakistan, Afghanistan's eastern neighbor, allowed military planes to fly in its airspace on specific routes, but no Pakistani air bases were used in the attacks, U.S. military officials told Fox News.
But some Muslim leaders in Pakistan condemned the attacks, saying they targeted innocent Afghan civilians and warning that the U.S. would find itself in a difficult place with the Muslim world.
Musharraf's spokesman said there could be a backlash from Islamic extremists in Pakistan for supporting the U.S., and that many locations in the country are on a heightened state of alert.
In Indonesia, a hardline Muslim group on Monday called for Muslims to "besiege" the U.S. embassy in Jakarta, and threatened to hunt down foreigners and destroy foreign interests unless the government cuts off ties with the U.S.
Israeli Foreign Minister Shimon Peres called the U.S. attack on Afghanistan on Sunday a "brave decision" by President George W. Bush.
"I think that all us, first of all, are praying for the welfare of the American army and its allies," he said on Israel's Channel Two television.
A governmental delegation that planned to visit Washington later in the week will not do so, but not for security reasons, Tel Aviv said. The Israeli government was cancelling the trip because it did not want to distract from the matter at hand, it said.
China's official news service, Xinhua, issued a statement saying that the country opposed terrorism in any form, and that Beijing hoped there would be no civilian casualties.
In Tokyo, Japanese Prime Minister Junichiro Koizumi said early on Monday that Japan supported the air strikes against Afghanistan and added that he was ordering a tightening of security nationwide.
Italian Prime Minister Silvio Berlusconi also publicly supported the attacks.
The U.S. had kept its allies abreast of its planes, with Bush telephoning other world leaders an hour or so before the strikes were launched. Spokesmen for Putin, Chirac, Canadian Prime Minister Jean Chretien and Schroeder all said their nation's leaders were informed that the airstrikes were imminent.
Though it was not clear how far in advance Musharraf knew of the coming bombardment, Pakistan had begun moving the 20,000 Afghan refugees just on their side of the Afghan border away from the boundary just before nightfall, several hours before the attacks
In a sign of the changing times, Russian air defense units did not go to a heightened alert status after the bombing, staying instead in normal mode. In the Cold War years, Soviet air defenses were automatically put on heightened alert following any military activity by the United States.
The Associated Press contributed to this report.