The Archbishop of Mandalay, his staff and around 20 diocesan priests have been placed under incommunicado house arrest.
The arrest happened on Friday April 8, after roughly 40 soldiers from the Myanmar/Burma army forcibly occupied the Sacred Heart Cathedral where they were holding a Lenten prayer service.
The soldiers reportedly entered the church and detained the congregation for about three hours.
On April 9, the Catholic News Agency reported that Archbishop Marco Win Tin, Vicar General Mgr Domenic Kyo Du and their staff, together with around 20 diocesan priests, were still being held in the cathedral compound.
Christian Solidarity Worldwide's (CSW) Senior Analyst for East Asia, Benedict Rogers, said: "This appalling raid on the Sacred Heart Cathedral in Mandalay is one of the latest indicators of the continued antagonism of the Myanmar army towards religious groups in the country.
"We call on the army to release all those currently held in the cathedral compound, and to cease its harassment of religious communities and other civilians. CSW continues to call for the urgent restoration of democracy in Myanmar, and for the immediate and unconditional release of all religious and political prisoners."
Thirty soldiers remained in the cathedral overnight, claiming that they were searching for weapons after an informant alleged that Archbishop Win Tin was supplying weapons to rebels throughout the country. However, no weapons were found on the premises.