BEIJING-- The world on Sunday marked the 10th anniversary of the tragic Sept. 11 terror attacks through various means, vowing to continue to fight terrorism.

Memorial service was held at the National September 11 Memorial, site of the destroyed World Trade Center twin towers in New York, to remember the 10th anniversary, amid tightened security.

U.S. President Barack Obama, former President George W. Bush, New York state and city officials joined family members of victims of the 2001 and 1993 attacks at the reflecting pools, which were built over the towers' footprints.

The ceremony, which is expected to last more than four hours, will pause six times -- twice to mark the times when each of the twin towers was hit, twice to mark the time when each tower fell. The other two pauses are to mark the times when the Pentagon was hit and when Flight 93 crashed in Shanksville, Pennsylvania.

Then families of the victims started reading of the names, which were carved into stone at the reflecting pools.

The ceremony was held amid heightened security across the city. In addition to security measures in and around the site of memorial service, police have established checkpoints at major transit hubs, bridges, tunnels and landmarks.

There were earlier reports about intelligence that al-Qaeda may have sent three operatives into the United States to detonate a car or truck bomb in New York or Washington, D.C.

On Sept. 11, 2001, nearly 3,000 people died when terrorists crashed hijacked airplanes into the twin towers, the Pentagon in Virginia, and a field in Shanksville. Six people were killed in the Feb. 26, 1993 car bombing at the World Trade Center.

Meanwhile, war-weary Kabulis passed a peaceful day on Sunday amid tight security as the United States and allied nations fighting in Afghanistan commemorated the disastrous Sept. 11 attacks.

The Afghan government has beefed up security in the capital city Kabul over the past couple of days.

Although no major attacks were reported in the fortified capital, Taliban militants carried out a deadly suicide truck bomb attack against a NATO military base in Kabul's neighboring province Wardak, killing two civilians and injuring 75 NATO soldiers and 25 civilians.

In Germany, President Christian Wulff attended a ceremony to pay condolence to the victims of the Sept. 11 attacks.

The commemoration in Berlin started with an ecumenical memorial service at the American Church.

All attendants stood in a minute of silent tribute at 2:46 p.m. local time (1246 GMT), the very moment when the first plane hit the World Trade Center in New York 10 years ago, to mourn the 3,000 victims who lost their lives during the terror attacks.

Other commemoration activities included a party at Brandenburg Gate featuring young people from different religious backgrounds and a memorial service at the Berlin Cathedral in the afternoon.

Marking the anniversary, Israeli Prime Minister Benjamin Netanyahu warned of growing radicalism and threat of militants obtaining nuclear weapons.

During the weekly cabinet session, Netanyahu said the world is still in danger and in fact is in the middle of a war.

"We are in this struggle, the struggle against terrorism, and while there is no doubt that this is terrorism, it is a tool of war. This is not a conventional war, and the struggle is not over," Netanyahu told ministers.

Senior Israeli and American officials took part in a memorial ceremony at a 9/11 memorial site near Jerusalem in the afternoon to commemorate the 3,000 victims.

Australian Prime Minister Julia Gillard joined the U.S. ambassador to Australia at a public 9/11 anniversary ceremony in Canberra.

The twilight ceremony on the shores of Lake Burley Griffin featured a flag party from the Australian Federal Police and the U.S. Marine Corps.

Hundreds of Australians lit candles to remember the victims of the terrorist attacks, and observed a minute's silence.

Foreign Minister Kevin Rudd marked the anniversary of the terrorist attacks with a ceremony at the War Memorial in Canberra.

In China, most Beijing-based newspapers carried articles to mark the anniversary, but just as they usually did for an international news.

Many leading newspapers put the 9/11 anniversary story on their international news page, mourning the dead and denouncing terrorist activities.

The People's Daily, China's leading newspaper, published a news story titled "U.S. starts serial events to mark the ten anniversary of 9/11," which covered U.S. President Obama's weekly radio and Internet address, responses from the United Nations, the European Union and other countries.

China's Twitter-like Weibo launched an on-line campaign to mark the 9/11, named "Say goodbye to terror with peace." It appealed to Netizens to post a microblog writing "peace" in their native languages.