The former Soviet republic, now a member of NATO and the European Union, has a 214-kilometre (133-mile) border with Russia, and has been one of Ukraine's most reliable supporters since Russia's invasion.

"We call on everyone during the big clean-up, but also afterwards, to ensure that your cellars and your basements can be used as shelters in case of emergencies," said Vilnis Kirsis, mayor of the capital Riga.

He said in a communique that municipal employees would do the same for buildings belonging to the city.

Gints Reinsons, head of a Riga civil defence commission, said "the basements of public buildings, schools, retirement homes, hospitals, and town halls will be inspected by the authorities who will prepare them to serve as hiding places in the event of an attack."

He told the TV24 station that the goal was to prepare a hundred anti-bomb shelters a month through the end of the year.

In March, Latvian Prime Minister Evika Silina compared Russia to an unpredictable drunk.

"We live next to a neighbour who, shall we say, is like an alcoholic or drug addict whose actions we cannot predict," she told public radio.

Since 2008, thousands of Latvians have gathered each spring to participate in a national clean-up day, a tradition that has now been followed by Baltic neighbours Lithuania and Estonia.

Besides collecting trash, Latvians also use the day to plant trees and fix up parks and public spaces.