The US embassy in Riga on Monday warned of a terrorist threat to American citizens in Latvia.

The embassy said children could be victims and that terrorists may target schools, hospitals, churches, tourist hotspots, transport hubs and other locations.

“Terrorists may employ a variety of tactics, such as violent assaults and kidnappings,” the US embassy in Latvia said on its website.

“In the past they have used knives, guns and vehicles as ramming devices,” it added.

The US embassy in Riga urged American citizens in Latvia to be careful, suggesting they stay alert in public spaces, keep a low profile and report social media threats to local authorities.

The embassy did not explain why it had issued the warning.

But Poland’s niezalezna.pl website said it could be connected to a planned mass gathering on May 9 to commemorate the end of World War II. The event is organised annually in Riga by the country’s Russian minority.

The Polish website also drew a link to the March 4 poisoning of Russian ex-spy Sergei Skripal.

British tabloid Sunday People said that British counter-terror police officers suspect that a 54-year-old former Russian Federal Security Service spy was connected to the attack on Skripal.

Meanwhile, the Mirror website said the spy, who goes by the alias "Gordon", worked in Latvia in the early 1990s.

It also said that Gordon may also go by the alias Mihails Savickis and two other names. (vb/pk)