A terse statement issued by the U.S. Embassy in Turkmenistan said students studying at American-affiliated universities in Bulgaria and Kyrgyzstan were denied permission to leave the country last week.
"We are dismayed by the government of Turkmenistan's continued denial of freedom of movement for ... Turkmen students," the statement said.
The former Soviet nation has been barring students studying at the American University of Central Asia, in Kyrgyzstan, from leaving the country since July, prompting many to seek a transfer to the university's Bulgarian branch.
Turkmenistan's secretive authorities have issued no public statements about the travel ban policy or the reasons behind it.
U.S. criticism of Turkmen government policy comes just weeks after a high-profile meeting in the United States between Turkmen President Gurbanguli Berdymukhamedov and U.S. Secretary of State Hillary Rodham Clinton.
Embassy officials in the Turkmen capital, Ashgabat, said the travel ban issue was raised during the meeting.
But "despite stating multiple times that it did not oppose the students transferring from the American University of Central Asia and traveling to the American University in Bulgaria, Turkmenistan denied the students exit on Friday," the embassy's statement said.
More than 50 students enrolled with U.S.-sponsored study programs have been affected by the travel ban.
Efforts to stop students from studying abroad are reminiscent of the draconian policies of late dictator Saparmurat Niyazov, who died in late 2006.
Educational standards withered under Niyazov, who made the study of his spiritual guide, the Rukhnama, obligatory for students at all levels. Basic education was cut to nine years from 10 years, while higher education was reduced to two years from five.
Growing numbers of people in Turkmenistan have begun to apply to study in the U.S. and at U.S.-affiliated universities over the past two years. Aspiring students still face official pressure not to enroll in foreign exchange programs, however, despite tentative Turkmen commitments to open up their country.
Berdymukhamedov became president in 2007.