The Syrian Arab Red Crescent estimates 2.5 million people are internally displaced within Syria by civil war, doubling the previous figure of 1.2 million used by aid agencies, the United Nations refugee agency said.

"The figure they are using is 2.5 million," Melissa Fleming, chief spokeswoman of the UN High Commissioner for Refugees (UNHCR), told a news briefing in Geneva.

"If anything, they believe it could be more, this is a very conservative estimate.

"So people are moving, really on the run, hiding. They are difficult to count and access."

The United Nations said on Friday that up to 4 million people inside Syria will need humanitarian aid by early next year when the country is in the grip of winter, up from 2.5 million now whose needs are not fully met.

The UNHCR has temporarily withdrawn about half of its 12 staff from north-eastern Hassaka province due to fierce fighting and insecurity that has resulted in the loss of some aid supplies and driven more Syrian Kurds into Iraq, Ms Fleming said.

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The United States military will station a powerful radar and a space telescope in Australia as part of a major refocusing of priorities towards Asia.

The deal calls for the first deployment of a US Air Force C-band radar in the southern hemisphere, allowing the Americans to better track space debris.

The agreement came during the annual defence talks between the two countries, held in Perth.

They were attended by US secretary of state Hillary Clinton and defence secretary Leon Panetta along with their Australian counterparts Bob Carr and Stephen Smith.

Mr Smith, the Defence Minister, says the two countries have been discussing space issues at the AUSMIN meetings for several years.

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