By Damian Grammaticas BBC correspondent in Riga

No campaigners say Latvia's sovereignty is too precious to give away

Speaking at a polling station in the capital Riga, President Vaira Vike-Freiberga said she believed over 60% Latvians would follow her lead and vote Yes to Europe.

But the No campaign maintains it could still cause an upset.

It appeals to Latvians' nationalism, urging them not to cede to Brussels any of the sovereignty they have only recently won back from Moscow.

Euro-sceptics say Latvia's 2.5 million people will suffer economically, as the country is the poorest of the candidate nations to vote on the EU accession.

For Latvia, it is putting the final full-stop to the sequels of the Second World War and wiping out forever the divisions on the map of Europe Latvian President Vaira Vike-Freiberga

The others - including Latvia's Baltic neighbours Lithuania and Estonia - have all decided in favour, but Latvia is perhaps the most Euro-sceptic of the candidates.

It lost its independence in World War II but regained it with the collapse of the Soviet Union in the early 1990s.

Symbolic vote

Polls opened in Latvia at 0700 local time (0400GMT) on Saturday, and will remain open until 2200 local time (1900GMT).

Just after casting her vote, President Vike-Freiberga looked in confident mood.

She said voting for Europe would help Latvia cement its transition to a democratic, market economy and mark a decisive break with the past.

"It means the end of years of hard work on our part to fulfil the criteria for the EU membership," the president said.

"But it means more than that symbolically.

"For Latvia, it is putting the final full-stop to the sequels of the Second World War and wiping out forever the divisions on the map of Europe that the odious Molotov-Ribbentrop Pact of 1939 had placed there."

If Latvia follows suit, the EU's expansion to take in former Soviet states will be complete.

The EU will stretch as far as Russia's border.