Hundreds of people have filed into St Andrew's Cathedral to pray for the injured and bereaved in the Paris Black Friday attacks.

Archbishop Glenn Davies told the congregation that after the Lindt siege, Sydney-siders feel for the people of Paris.

"We in the city of Sydney know to some measure this pain, though we have not suffered the loss of life to this extent" Dr Davies said.

"This service of sorrow and prayer is one small measure of our response - to come and mourn and to stand shoulder to shoulder with the people of Paris, the people of France."

"The attack on Charlie Hebdo in February this year, where 12 people were killed, you would have thought would be sufficient for one city to endure," he said.

"Now, 10 times that number have been shot down in a violent attack upon the citizens of Paris; a barbaric, senseless attack, upon not just the Parisians and tourists who were caught within its wake, but a symbolic attack upon all humanity, and upon the very essence of freedom. We are in a world where safety is under threat." (listen)

Taking part in the service were Premier Mike Baird, the NSW Governor, General David Hurley and the French ambassador Christophe Lecourtier, who read from Revelation 21.

The NSW Police Force was represented by  Deputy Commissioner Nick Kaldas.

Archbishop Davies read the 23rd Psalm in French and the congregation prayed the Lord's Prayer in both French and English.

The service finished with the French national anthem. The French flag has been at half-mast at the cathedral since Saturday when news reached Sydney of the shootings.

More than 120 people were murdered and hundreds injured in co-ordinated attacks in Paris on Friday 13th November.