Russia has developed the capability to launch an attack on the Baltic states with as little as 24 hours' notice, limiting NATO's options to respond other than to have military forces already deployed in the region, Lithuania's intelligence service said on Monday.

Axar.az reports that Lithuania, Latvia and Estonia, annexed by the Soviet Union in the 1940s but now part of both NATO and the European Union, have been increasingly nervous since the Russian takeover of Crimea in 2014.

The Lithuanian intelligence service said in its annual threat assessment that Russia had upgraded its military in the Kaliningrad region last year, reducing lead times for any attack and potentially preventing NATO reinforcements.

The Russian upgrade included Su-30 fighter aircraft and missile systems allowing ships to be targeted almost anywhere in the Baltic Sea.

"This is a signal to NATO to improve its decision speed," Lithuanian Defence Minister Raimundas Karoblis told reporters on the sidelines of the presentation of the report. "NATO's reaction time is not as fast as we would like it to be."

Kremlin spokesman Dmitry Peskov dismissed the concerns as a display of anti-Russian sentiment.

"There is total Russophobia, hysterical Russophobia going on," he said at a daily conference call with reporters.

"Moscow has always supported good relations with the Baltic states," he said.