Obama says US cooperation with Pakistan helped track bin Laden down and that he has called president Zardari.
Both presidents agree that this is a good and historic day in both their histories.
Al Jazeera correspondent says operation took place near Abbottabad and that helicopters circled the compound where bin Laden was reportedly hiding.
A senior Pakistani intelligence official confirmed on Monday that Osama bin Laden, the mastermind of the September 11, 2001 attacks, had been killed.
US media quoted sources as saying that Bin Laden was killed in an operation based on actionable US intelligence targeting a mansion in abbotabad.
Obama was imminently to address Americans in a highly unusual Sunday night appearance on television.
The death of Bin Laden will raise huge questions about the future shape of al Qaeda and also have steep implications for US security and foreign policy 10 years into a global anti-terror campaign.
A helicopter crashed in Abbottabad near the Pakistan Military Academy Kakul late on Sunday night, police sources said.
The chopper was seen flying low before it crashed, locals said. The sound of gunfire and two small blasts was heard before a massive explosion, sources said.
They added that the third blast damaged windowpanes of the area houses. This was stated to be the first incident of its kind in Abbottabad at night.
The sources said the helicopter fell down in a plot in Sikandarbad, a populated area of the city, spreading panic through the neighbourhood.
The sound of the explosion was heard as far afield as 10 kilometres, the sources added.
