"Thirty international search and rescue teams are on alert, they are monitoring the situation and ready to help should Japan request aid," said Elisabeth Byrs, spokeswoman of the UN Office for the Coordination of Humanitarian Affairs.

"The UN stands ready to help," she added.

At least eight people were reported killed after a huge earthquake of magnitude 8.9 rocked Japan and tsunamis up to 10 metres (33 feet) high slammed into its Pacific coastline on Friday.