Prime Minister David Cameron has tweeted:
I'm appalled by the murder of a Palestinian teenager. The loss of four boys this week is a terrible reminder of the need for lasting peace.
More top news
Jeremy Hunt has rejected Professor Stephen Hawking's claim that he "abused" scientific research to justify the creation of a seven-day NHS.
Showers in the north, perhaps turning heavy at times but becoming drier in the south towards the afternoon.
Police have stepped up their search for Younes Abouyaaqoub, believed to be at the centre of the investigation into the Las Ramblas attack.