Half of the world's 10.5 million refugees are living in urban centres, driving up living costs and increasing the risk of tension with local populations, the UN refugee agency said on Monday.

Antonio Guterres, the UN High Commissioner for Refugees (UNHCR), said the arrival of large numbers of displaced people in crowded cities was pushing up the costs of food and accommodation and making it more difficult for local populations to scrape by.

The resultant pressure 'can create tensions between local and refugee populations, and in worst cases, can fuel xenophobia with catastrophic results,' he said.

Kabul has grown sevenfold since 2001, the UNHCR said, mainly because of large numbers of displaced people from Iran and Pakistan, as well as uprooted people within Afghanistan who have flocked to the capital.

Armed conflict has also driven hundreds of thousands to Bogota in Colombia and Abidjan in Ivory Coast, where many are forced to live in 'ill-serviced slum areas' that lack the basic aid often associated with UN camps, the agency said.

Damascus in Syria and Amman in Jordan have also become a sanctuary for Iraqis who were forced to flee the violence in their country following the 2003 US-led invasion.

'We need to abandon the outmoded image that most refugees live in sprawling camps of UNHCR tents,' said Guterres, a former Portuguese prime minister.

He said many urban-dwelling refugees lacked access to medical care or other assistance and were subject to exploitation because they did jobs that were unregulated. – Reuters