Rohingya sources said the insurgent group ARSA was behind the shootings of Syed Hossain and Abu Taleb.
The regime last month awarded titles to leaders of seven of the 10 groups planning to attend talks, prompting speculation it was looking to secure their participation.
As the rest of the country suffers crippling power and water shortages exacerbated by fuel price hikes, life in Naypyitaw is relatively normal.
The disastrous events triggered by the coup have convinced Myanmar’s people there can be no place for the current military institution in their country’s future.
Twelve of those have died while in the regime’s custody, seven while being tortured during interrogation, said the party, which won last year’s election in a landslide.
Courts are preparing to hand down penalties in the corruption, incitement and other cases the junta has brought against scores of elected leaders since the coup.
Member countries urged the regime to implement the bloc’s five-point consensus on Myanmar, as several leaders backed chair Brunei’s decision to exclude Min Aung Hlaing.