US President Barack Obama and his predecessor George W. Bush on sunday led the world in mourning the nearly 3,000 victims of the 9/11 terror attacks 10 years ago. Moments of silence were observed at the exact times when the planes crashed in the Twin Towers, the Pentagon and in Pennsylvania. The streets of New York wore a deserted look with only a few people on the sides of the roads. George Bush also read from a letter Abraham Lincoln wrote to a civil war widow 150 years ago. Security has been put on high alert as the US is marking the 10th anniversary of the attacks.Earlier, President Barack Obama paid tributes to those who died in the terror attacks and to those who tried saving others. Obama and his wife Michelle also visited the Arlington National Cemetery, and also paid their respects to the US military personnel who died in the wars in Iraq and Afghanistan. President Obama said the United States is stronger than it was ten years ago, and the Al-Qaida, which carried out the attacks, is on the path to defeat.Relatives of victims gathered in a field in Pennsylvania to watch the former President George Bush and current Vice-President Joe Biden unveil a memorial to those who died in one of the hijacked planes. In Britain, Survivors and families of some of the 67 Britons killed during the attacks on New York and Washington DC gathered at an early morning service of remembrance and reconciliation in the Grosvenor Chapel in central London.Remembrance and memorial services are also being held in different countries for the nearly 3000 victims of the terror attack.