The eventual victors of the Group B fixture went into half-time 4-2 ahead and the two teams exchanged penalties after the break.
China managed to reduce the deficit to just one point with seven minutes left, before giving away a team penalty for delaying the game. Sayahi then scored another three goals to cap his extraordinary performance before being substituted late on.
The group’s other encounters saw the Republic of Korea come away with a 4-3 victory over Algeria, while Belgium were 4-2 winners over Canada.
Lithuania were the biggest winners in Group A as they marched to an 11-1 victory over Great Britain in the event’s curtain-raiser.
With four goals to his name, Genrik Pavliukianec was the man who did the damage for the Lithuanians, sending out a clear warning signal to their rivals in the competition.
Great Britain’s David Knott admitted his side were taken by surprise, saying: 'We didn't quite know what to expect. They were faster than we anticipated. It was a tough game.'
After a one-sided opener to the competition came a closely-fought battle between Finland and Brazil - the latter emerging as 6-5 victors - while Turkey were convincing 9-2 winners over Sweden in the group’s other match.
China got their women’s Goalball campaign off to a strong start with a 7-1 victory over Great Britain - a match which saw Wang Ruixue show her class by scoring four goals for her country.
Group C’s other encounter was a low-scoring affair as Brazil emerged as narrow 2-0 winners over Denmark, while the USA kicked off their Group D campaign with a 5-1 victory over Sweden.
Appearing in her sixth Paralympic Games, Jen Armbruster showed that she is still a force to be reckoned with by scoring three goals for the USA.