The messages were quickly removed, but the information was sent to the Secret Service`s internet threat desk.
F-16 fighter jets scrambled twice after reports of air passengers acting suspiciously on two flights.
Barack Obama and George W Bush stood together in New York for the main ceremony at the site of destroyed Twin Towers.
US President honoured the legacy of September 11 victims by personally tracing the trail of terrorist attacks.
Pope Benedict XVI appealed to the world to resist what he called the temptation toward hatred.
An editorial in the Dawn said that Pakistan was stuck with a pre-9/11 mindset in a post-9/11 world.
The US has already had bolstered security nationwide before the upcoming anniversary.
Pakistan has made an attempt to reach out to the American public, telling them that it has been a victim of terrorism.
With federal officials warning of a new terrorism scare, Barack Obama has called for a heightened state of vigilance.
Day in Pics: 20th December
Showbiz World - December 20, 2014
People Magazine Awards 2014