The Swiss team, seeded 16th for the World Tour event, took the opening set before the Brazilian duo hit back to send the contest into a decider.

Despite seemingly having the momentum in their favour, top seeds Bednarczuk and Seixas were unable to deal with the power from their opponents in the third as Heidrich and Zumkehr closed out a hard-fought 23-21, 21-23, 16-14 success in a match which lasted four minutes shy of an hour.

The result sees them earn a bye in the next round of the tournament and they will therefore progress straight into the last 16 of the main draw.

“This was really a very important match for us,” Zumkehr said.

“First of all, we had never beaten Agatha and Barbara. 

“Secondly, we have our best finish in Moscow in four events.

“Finally, we add points to our Olympic ranking total - a lot of pluses for us today.”

Elsewhere in the women’s competition, American pair April Ross and partner Kerri-Walsh Jennings, a three-time Olympic champion who will go for a fourth straight gold at Rio 2016, also topped their pool as they picked up three victories.

The third seeds were pushed all the way in the opening set of their final group contest against Switzerland’s Anouk Vergé-Dépré and Isabelle Forrer before they saw out a 31-29, 21-16 triumph in Pool C.

While their female counterparts were on the hands of a shock reverse, men’s top seeds Alison Cerutti and Bruno Oscar Schmidt of Brazil secured two wins to end the group phase with a 100 per cent record.

They started the day with a 21-18, 26-24 victory against World Tour leaders Piotr Kantor and Bartosz Losiak of Poland before they comfortably overcame Canada’s Josh Binstock and Sam Schachter 21-14, 21-14.

“That was a good win for us over a young team that won the Rio Grand Slam in March,” Schmidt said following the triumph over the Polish duo.

“The Polish kids have played a lot of events this year to get ready for the Olympics.

“We are taking a different approach with this event being like our first in a series of tournaments to prepare for Rio.”