The incident left a seven-year-old boy and an 82-year-old woman dead, according to the mayor's office in Quito, updating an earlier toll of one fatality.
The blast occurred at 11:11 pm on Sunday when leaking gas ignited, the mayor's office said.
Authorities added that the victims were dining in the restaurant at the time of the explosion.
It also left about a dozen cars with windshield and body damage, and caused windows to vibrate within two blocks of the area.