US President Obama has nominated Senator Chuck Hagel as his new defence secretary.
The former Republican senator for Nebraska will take over the top Pentagon job from Leon Panetta if his appointment is confirmed by the Senate.
President Obama said that US troops would see in Senator Hagel a "decorated combat veteran of character and strength".
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Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.
As temperatures climb through the day, the warmest spots are likely to be across western parts of Northern Ireland and western Scotland.