A government source speaking on condition of anonymity told AFP the measure was meant to "track the contingent praying at the mosque, to identify among believers potential followers of Salafism.”
The equipment will be installed at the expense of the mosques and their congregations, a spokesperson of the Dushanbe city administration said.
The secular government of this Central Asian country, which looks to former master Russia for security guarantees, is renowned for its anti-Islamic rhetoric and policies.
Tajikistan shaves beards off 13,000 men to tackle extremism
The government is currently trying members of the opposition Islamic Renaissance Party of Tajikistan (IRPT) on an array of charges including attempting to overthrow the constitutional order and organising a criminal group.
Authorities have accused party members of fanning a wave of unrest that killed dozens of people last year.
A number of international organisations and Western countries have raised concerns that Tajikistan is using the threat of international terror as a pretext to clamp down on the opposition.
The Tajik parliament in January voted to ban "foreign names" for babies as the popularity of Arabic names in the Persian-speaking country has grown.
Tajikistan says more than a thousand of its citizens are fighting in the ranks of the Islamic State group in Iraq and Syria, including women and children.
The interior ministry's special forces chief last year made a shock defection to IS and appeared in a propaganda video criticising the government's harsh anti-Islam policies.
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