INTERNATIONAL: In the Black Sea port city of Odessa, walls of sandbags several meters high surround the monument to Duke de Richelieu, the early 19th century governor who helped transform the Black Sea port into a modern city.

The famous monument on Primorsky Boulevard was erected in 1828 and is a popular site for tourists.

After Russian forces began attacking Ukrainian cities such as Mariupol, museums and local authorities have rushed to protect their heritage, stowing away precious artworks, religious icons, and fortifying national monuments.

Odessa’s famous 19th century Italian baroque opera house, which survived the second world war, is also surrounded on all sides by sandbag barriers, while a military vehicle is parked across its entrance.

Soldiers are on guard around the historical landmark, and on the rest of the streets and in the port of the city.

As air raid sirens were heard on Thursday, the streets, filled with anti-tank barriers, emptied, save for soldiers and reservists.

"Every war is a disaster....we hope it is going to end in the closest future," said 28-year old soldier Andriy. Another soldier on patrol has stopped to play a few notes on a piano on the street.

The city fears an imminent attack, possibly by sea. Its Black Sea port is a crucial commercial and transport hub for the country.

Residents have been evacuating the city, although a spokeswoman for the mayor has said they had no statistics on how many had left.