The World Health Organisation on Wednesday said it was asking countries that took "significantly different" measures to combat swine flu, such as restricting international travel, to justify their actions.
"Countries adopting measures which are significantly different or which interfere with international traffic must provide WHO with the public health rationale and relevant scientific information for these measures," said Gregory Hartl, spokesman for the WHO.
Without specifying countries, Hartl added that the UN health agency has "begun the process of getting more information from a number of countries... on the public health rationale of their action."
Amid the influenza A(H1N1) scare, some countries, including Argentina, Cuba, Ecuador, Peru and China, have suspended flights from Mexico, the epicentre of the outbreak.
China's decision to quarantine Mexicans and suspend flights to and from Mexico sparked a diplomatic uproar, with a chartered Mexican jet arriving in Beijing Wednesday to fly scores of its nationals home.