The Australian defence vessel, Ocean Shield has detected an oil slick in the Indian Ocean within the search area for flight MH370.

Joint Agency Coordination Centre (JACC) head Angus Houston said the oil slick is approximately 5,500 meters downwind and downsea from the vicinity of the signals picked up by the vessel earlier.

"A sample of about 2 liters have been collected and we have a number of days before it lands ashore and conclusively tested," he said at a press conference in Perth today.

However, Houston cautioned that the source of oil is yet to be determined.