Puerto Rican singer Ricky Martin has been in Phuket, Thailand, with two film crews and an entourage filling four vans to find out what his charity foundation could do to help.

"It's all about the most vulnerable, the children of Phuket," Martin said. "It's all about learning and seeing which ways I can help."

But visits like these, to be followed this weekend by the arrivals of the prime ministers of Sweden, Finland, Norway and Canada, create animated debate among aid workers about whether they are useful or mere distractions.

To experienced senior officials of aid organisations who know only too well how quickly public interest in horrifying natural disasters fades, such visits have to be accommodated as they mount the biggest aid operation in world history.

"Public interest remains, but it needs to be stimulated a little so people are aware of what's going on," Unicef spokesman John Budd said in Indonesia.