An Isil smartphone app designed to indoctrinate young children as jihadists allows them to play games carrying out 9/11-style attacks on Western landmarks including Big Ben.

The computer app which also teaches youngsters to spell words like grenade and rocket is part of a wider attempt to pass the extremist ideology on to the next generation, the spokesman for the international coalition fighting the militants said.

The app which was released earlier this year has been recently updated to include games to destroy targets including the Statue of Liberty and the Eiffel Tower, he said.