The three latest deaths are all patients with chronic diseases, said Tran Thanh Tung, director of Sa Dec General Hospital in Sa Dec Town.
They are two women aged 52 and 43 and a 65-year-old man.
They had type 2 diabetes, chronic kidney failure, stroke and hypertension prior to Covid-19.
None of them has been registered into the national death tally by the Health Ministry.
Since July 2 when the first Covid-19 died, Dong Thap has recorded 11 more Covid-19 fatalities.
But the Ministry has so far just confirmed two Covid-19 deaths in Dong Thap.
For the ongoing Covid-19 wave that hit Vietnam in late April, Dong Thap has recorded 325 cases, as announced by the Health Ministry.
The province has applied social distancing measures in its Sa Dec Town, Chau Thanh and Lai Vung districts and imposed lockdown at several areas in Chau Thanh District.
Nationwide, 102 Covid-19 patients have died, including 67 in this wave.