Lithuanian President Dalia Grybauskaite has emerged as the clear leader in elections, but looks likely to face a run-off to secure a second term.
With about 95% of the ballots counted, the 58-year-old secured nearly 46% of the vote, election officials said.
Her nearest rival, European Parliament member Zigmantas Balcytis, won 14%.
The run-off is planned for 25 May. The elections come amid rising security concerns in the region after Russia's annexation of Crimea from Ukraine.
"Europe must understand that Russia is trying to redraw the post-war map and borders," Ms Grybauskaite said before Sunday's vote.
"First, it's Ukraine, Moldova will be next and, finally, it can reach the Baltic states and Poland. This is serious threat to our region."
Some 2.5m people were eligible to cast their ballots.
Ms Grybauskaite, the tough-talking karate black belt, needed 50% of the vote to avoid the second round.
With Ms Grybauskaite seen by many as a hot favourite, critics said the campaigning lacked energy.
"I have never seen in any country such a dull election campaign," former President Valdas Adamkus was quoted as saying by the Associated Press news agency.
In all, seven candidates were competing in the presidential race.