World News Update, what you need to know

The so-called Islamic State has murdered a second American reporter, releasing another video Tuesday showing a masked militant with a British accent cutting the throat of a US captive.

ELSEWHERE:

UNITED NATIONS, United States - International medical agency Medecins sans Frontieres says the world is "losing the battle" to contain Ebola and has called for a global biological disaster response to get aid and personnel to west Africa.

BAMAKO - Four United Nations peacekeepers have been killed when their truck was blown up in rebel-infested northeastern Mali.

WASHINGTON, Sept 2 AFP - A US air raid in Somalia targeted the leader of Somalia's Shebab militants but it remained unclear if the top commander was killed in the strike.

NEW YORK - Apple says a "targeted attack" on some user accounts led to the release of nude celebrity photos but that it found no breach of its cloud storage system.

LONDON - A piece of criminal history can be yours for STG250 million ($A456 million) - London's world-famous Scotland Yard police force has put its headquarters up for sale.