The Latvian Armed Forces later announced on Thursday that the threat had ended, without providing further detail.
Ukraine has in recent months stepped up its long-range drone attacks on Russia, including in the Baltic Sea area, where several Ukrainian military drones have strayed into the airspace of NATO members Finland, Latvia, Lithuania and Estonia.
Kyiv has apologised for incursions and blamed Russian jamming of guidance signals for misdirecting its drones across borders.
Moscow says Ukraine is using NATO airspace to provide cover for its attacks on Russia, which Kyiv, NATO and the Baltic states strongly deny.
"As long as Russia's aggression in Ukraine continues, there is a possibility of repeated incidents where foreign unmanned aerial vehicles enter or approach Latvian airspace," the Latvian armed forces wrote on social media platform X.
One drone was confirmed to have crossed into Latvia from Belarus, a military spokesperson told broadcaster Latvian Television.
The Latvian government resigned last week over its handling of the incursions, and talks are ongoing on appointing a new cabinet.
The armed forces in a statement on Thursday warned residents in eastern Latvia, bordering Russia and Belarus, to seek shelter indoors while the incident was still ongoing.
On Tuesday, a NATO fighter jet shot down a suspected Ukrainian drone over neighbouring Estonia, and a similar airspace violation in Lithuania on Wednesday halted air traffic to its capital and forced its MPs to take shelter underground.
"They (Ukraine) certainly don't want their drones to end up on friendly territory for obvious reasons," Swedish Prime Minister Ulf Kristersson said on Thursday.
"Sometimes it's a matter of jamming. Sometimes it's a matter of other disturbances," he told a joint media conference with NATO Secretary-General Mark Rutte.
The Baltic states, all strong backers of Ukraine, have blamed the incidents on Moscow, saying it redirects Ukrainian drones from their intended targets in Russia, without providing evidence.
The Kremlin said on Wednesday it was monitoring the situation.
Poland's defence minister on Thursday said Ukraine must be very precise when using drones to avoid giving Russia the opportunity to interfere with their flight path.
European Commission chief Ursula von der Leyen on Wednesday said that Russian threats to the Baltic countries were "unacceptable" and would be seen as threats to the whole European Union.
