"We want the polling stations to stay open tonight, till midnight if necessary, " Mr. Alvi said.

WSJ: Karachi Beset by Political Strife

But markets are not open tonight and it is unusual for a business to react to a leak in this way.

BBC: Marks and Spencer's premature release

His rival Hillary Clinton has said she will not concede tonight, but is "open" to becoming Mr Obama's running mate.

BBC: Obama 'to win' party nomination

More than a hundred museums and institutes across the EU will be throwing open their doors to mark the event tonight, with some 300 researchers at the NHM staying late to discuss their work, answer questions, and give people a tour around the warren of backroom stores and laboratories.

BBC: Forensic science uncovered

This morning, Senior Advisor to the President David Plouffe sent a reminder to the White House email to tune into President Obama's State of the Union Address tonight and to watch the live Open for Questions event immediately following the speech.

WHITEHOUSE: Our Top Stories

It was there while singing on the BBC radio show In Town Tonight that Makeba met Harry Belafonte, who would open up the road to world stardom for her.

BBC: Obituary: Miriam 'Mama Africa' Makeba