"We cannot accept that [refugees] live in such miserable conditions, exposed... to violence and exploitation," said Filippo Grandi, during a visit to the Kara Tepe camp on the Greek island of Lesbos. "These living conditions need urgent improvement," he added. 

Filippo Grandi, the UN High Commissioner for Refugees, urged Greek and European authorities to act "urgently" to improve the situation faced by thousands of migrants on Greek islands and in camps. 

The Greek government has recently announced plans to fortify some camps on Lesbos, Samos, Chios, Kos and Leros, while simultaneously ensuring its borders are "air-tight" to stop further migration. 

Prime Minister Kyriakos Mitsotakis has also pledged to resettle over 4,000 unaccompanied children on the Greek mainland, after failing to persuade other EU states to accept many of them.

This was welcomed by Grandi who told the media he believed the PM "is very worried about children". 

But the visit came after several protests in Northern Greece, with locals hoping to block the relocation of asylum seekers to the area.