During the morning rush hour, a series of explosions have blasted in downtown London, killing at least two people and casualties (which include both the wounded and dead) were hovering near a hundred. The front of a double decker bus was sheared off in one explosion, while a number of explosions (anywhere from three to seven) hit between six Underground stations (Edgware Road, King's Cross, Liverpool Street, Russell Square, Aldgate East, Moorgate). People may still be trapped underground near the King's Cross station (here's an evacuation picture), which sounds awful as the London Underground tunnels are incredibly narrow and very deep underground. Prime Minister Tony Blair feels it's "reasonable" to suspect the explosions are terror-related, and he will be leaving the G8 conference in Scotland to check on the scene; the conference, however, will go on. Here's more from BBC News, and Londonist's breaking news updates show that the Underground explosions were related to "power surges" at first.
In terms of what's happening with U.S. Homeland Security, the national terror level is staying the same, but as always, the city's terror will be elevated. Police presence is being elevated around the NYC subway stations (as it is with the DC Metro). In May, there was a relatively small explosion in front of the British Consulate in Midtown, but no suspects have been found.
Update: Prime Minister Blair spoke again, from the G8 Conference, this time with all the other world leaders by his side, with President Bush and President Jacques Chriac at his immediate right and left.
There are photographs on Flickr - London Bomb Blasts pool.
Photograph from Reuters