(Adds comment from NATO Secretary-General)
VILNIUS, May 14 (Reuters) - Baltic states Lithuania, Latvia and Estonia are preparing an appeal to NATO command for a permanent presence of NATO troops on their territory to counter increased Russian air and naval activity, the Lithuanian army said on Thursday.
The states, all with ethnic Russian minorities, fear they could become a target of Kremlin pressure after a pro-Moscow rebellion in eastern Ukraine and President Vladimir Putin's declaration last year of an obligation to protect Russian speakers across the former Soviet Union.
"In reaction to the security situation in the region, as a measure of deterrence, chiefs of defence of the Baltic states will apply officially to Supreme NATO Allied Commander Europe (SACEUR) about permanent stationing of a brigade-sized NATO unit in the Baltic States," Lithuanian Army spokesman Mindaugas Neimontas said.
The Baltic states would ask, in a joint letter, for the brigade to consist of battalion-sized deployments of NATO troops in each of the countries, which would rotate on a NATO-approved schedule.
A NATO brigade typically numbers between 3,000 and 5,000 troops and is made up of several battalions.
NATO Secretary-General Jens Stoltenberg, speaking at a press conference at the end of a NATO foreign ministers' meeting in Turkey, said NATO had increased its air policing, as well as naval and ground presence, in the region.
"When we receive the letter, we will go carefully through the letter and assess the different proposals ... but I think it is a bit too early to comment on details and specifics."
NATO has recorded heightened activity by Russian military aircraft near their air space and there have been reports of suspected submarines in Swedish and Finnish waters.
A NATO summit in Wales last year agreed to beef up rotation of allied troops and their equipment in the region, but shied away from the setting up permanent bases of NATO troops in the three Baltic countries and Poland.
The United States keep a rotating presence of 150 troops in each of the Baltic States and Poland since April 2014, augmented by occasional shifts of similar-sized units from other NATO allies.
The Alliance remains divided on setting up permanent bases in the east as some states see it as counter to an existing agreement with Moscow.
The Baltic states of Estonia, Latvia and Lithuania, which were annexed by the Soviet Union in 1940 and were part of it until 1991, have been members of the European Union and NATO since 2004. (Reporting by Andrius Sytas in Vilnius, David Mardiste in Tallinn and Adrian Croft in Antalya; editing by Sven Nordenstam and Ralph Boulton)