A statement issued by the U.S. Embassy in Turkmenistan on Monday says students studying at U.S.-affiliated universities in Bulgaria and Kyrgyzstan were denied permission to leave the country last week.

Turkmenistan's secretive authorities have issued no public statements about the travel ban policy or what reasons may lie behind its implementation.

Efforts to stop students from studying abroad are reminiscent of the draconian policies of late dictator Saparmurat Niyazov, who died in late 2006.

President Gurbanguli Berdymukhamedov has made tentative commitments to open up the energy-rich former Soviet republic.