New Delhi, May 2 -- With summer holidays approaching, the United States has issued a 'Do Not Travel' advisory for as many as 21 countries. Among those listed are Russia, Ukraine, Iran, and Iraq. The US State Department classifies travel advisories into four levels, with 'Do Not Travel' being the most severe. While some of these warnings have been in place for several months, others have been introduced more recently.

This level applies to generally safe tourist destinations such as Japan, Bermuda, and the Cayman Islands. Travellers are advised to remain alert, although there are no specific threats at present.

Travellers should be more vigilant in countries like Saudi Arabia, China, and Spain. While travel remains possible, risks such a...