Deputy Prime Minister Nick Clegg described the Woolwich attack as "shocking and horrifying".
In a statement, he said: "This afternoon witnessed a shocking and horrifying murder on the streets of our capital.
"The whole nation's thoughts will be with the family and friends of the victim this evening.
"People across our country, whatever background they are from, will be united in condemning this attack and we will stand together, as we always do, in our response."
More top news
After a remarkably mild November, a notably mild start to the new month.
After a remarkably mild November, it's a similar set up into the start of December.
A transgender inmate has been found dead at Woodhill Prison in Milton Keynes.