Five Australians still missing in quake

Less than a week ago consular officials were trying to confirm the whereabouts of more than 140 Australians in areas affected by the quake and tsunami.

"We have now got that down to five," Foreign Minister Kevin Rudd told ABC Television.

"Our objective, of course, is to reduce that five down to zero and the team have been doing a fantastic job."

Mr Rudd rejected criticism of the way Japanese authorities had handled the disaster, saying the government was responding to appalling circumstances.

"If we were in their position ... that would go beyond the normal planning parameters of any disaster relief agency in most countries," he said, adding hundreds of thousands of people were seeking emergency food and shelter.

Australia and other nations still had open offers of assistance to Japan.

"If the Japanese wanted further help, I am sure they would advise us further," he said.

The Department of Foreign Affairs and Trade (DFAT) said an estimated 1000-1500 Australians remained in the greater Tokyo area.

Many Australians had already left Japan and there were plenty of seats still available on commercial flights heading for Australia.

Since Friday evening, hundreds of seats to Australia had gone unfilled, DFAT said in its Monday morning update of the situation in Japan.

"We continue to monitor the situation closely and if we need to add to availability, we have plans in place with Qantas allowing us to arrange extra flights within 24-48 hours."

The department said it was aware the UK had updated its travel advice and was distributing iodine tablets as a contingency measure against nuclear contamination.

"We will of course continue to closely monitor all potential health impacts caused by the current situation and are keeping all options under close review," it said.

Australians are advised not travel to Tokyo and northern Honshu unless it is essential.

Australians in those areas should leave unless their presence was essential.