Defense Ministry spokesman Faridoon Makhmadaliyev said Sunday's "terrorist act" had been carried out by militants linked to former warlords who fought against the government in a civil war in the 1990s.
"These are mercenaries of the Islamic Republic of Pakistan, the Islamic Republic of Afghanistan and the Chechen Republic of the Russian Federation who, under the guise of the sacred religion of Islam, are attempting to turn Tajikistan into an arena for feudal wars," he said.
"Twenty-three soldiers, including some officers of the Ministry of Defense and the National Guards, were shot dead yesterday in the Rasht valley."
Tajikistan, a secular but mainly Muslim country which shares a porous 1,340-km (840-mile) border with Afghanistan, is battling growing Islamist radicalism and has imprisoned more than 100 members of banned groups this year alone.
The ambush occurred in the Rasht district, 50 km (30 miles) from Tajikistan's border with Afghanistan and 180 km (110 miles) east of the capital, Dushanbe.
Troops had been traveling to the region to reinforce roadblocks in the north of the country, a month after prisoners including organizers of an alleged coup plot escaped from a detention center in Dushanbe.
Security sources told Reuters the escaped prisoners included citizens of Tajikistan, Afghanistan and Russia. Many were sentenced in August for organizing a coup in the poor former Soviet republic.
The Tajik news agency Asia-Plus, citing an unidentified security source, said 40 servicemen were killed in the ambush. Reuters could not immediately confirm the figure.
"So far I can only confirm that 23 were killed and 10 were wounded," a high-ranking government source told Reuters, on condition of anonymity.
He said the gun battle had ended and armored vehicles and reinforcements had been sent to the region. Defense Minister Sherali Khairulloyev flew by helicopter to the area on Sunday.
Tajik President Imomali Rakhmon left for New York hours before the attack to attend the UN General Assembly. A government spokesman said he had no plans to cut short the trip.
The poorest of five former Soviet republics in Central Asia, Tajikistan is viewed with interest by Russia and the United States because of its strategic location.
Last week, Tajikistan said it had killed at least 20 Taleban fighters and lost one officer in a clash on the Afghan border.
Tens of thousands were killed in the 1992-1997 civil war between factions reflecting overlapping political, religious and clan loyalties.
