Barack Obama, the US president, has laid a wreath at the Pentagon in memory of those who were killed in a series of attacks on the mainland on September 11 eight years ago.

Obama on Friday attended the memorial service at the headquarters of the department of defence in Washington, which was attacked along with the World Trade Centre in New York in 2001.”No turning of the season can diminish the pain and the loss of that day… No passage of time and no dark skies can ever dull the meaning of this moment,” Obama said, speaking of the day of attacks in which almost 3,000 people were killed in co-ordinated assaults by al-Qaeda.

The president said that maintaining a shared purpose to oppose “terrorism” would be the most effective way to stand against those who wish to strike the US.

“Let us renew our resolve against those who perpetrated this barbaric act and who plot against us still,” he said.

“In defence of our nation, we will never waver.”