Pope Francis has criticised the US military for naming the largest explosive in its arsenal the "mother of all bombs".

He was speaking weeks before he receives US President Donald Trump, who authorised the use of the bomb against ISIS militants in Afghanistan last month.

The 21,600lb (9,800kg) Massive Ordnance Air Blast (MOAB) explosive is nicknamed the "Mother Of All Bombs" because of its acronym and immense power.

The Pope told an audience of students at the Vatican: "I was ashamed when I heard the name.