The singer warned fans that Thair Orfahli would be in charge of his page, writing, "My feed won't be the same over the next day, @ThairDamascus is taking over. It's for a special cause. See you on the 19th #ShareHumanity."

Orfahli posted regular updates during a 16-hour period recounting his trip to Germany through Lebanon, Egypt and Italy, with messages including, "On a boat to Italy w/ (with) 234 other refugees and migrants. Their strength is unbelievable... I have no passport, no money, and no clothes. Nothing. But I am happy to be alive."

The takeover is part of a United Nations campaign called #ShareHumanity, in which social media users lend their accounts "to give a voice to the voiceless" in the run-up to World Humanitarian Day on 19 August (15).

Simpson says, "I'm getting behind #ShareHumanity because it's a way of showing that we haven't forgotten that there are millions living in humanitarian crises... I hope others will join us in this massive display of public support calling for a more humane world."

Jess Origliasso of Australian rock duo The Veronicas has also joined the campaign.