Two victims of the deadly siege in Sydney were being remembered at private memorial services, a week after a gunman took them hostage inside a city cafe.

The memorial for Tori Johnson was held at a church close to the Lindt Chocolat Cafe, where he and 17 others were taken hostage on December 15 by shotgun-wielding Man Haron Monis, a 50-year-old Iranian-born, self-styled cleric with a long criminal history.

The stand-off ended 16 hours later when police stormed the cafe in a barrage of gunfire to free the captives.

Mr Johnson, the cafe's 34-year-old manager, and 38-year-old lawyer Katrina Dawson were killed, along with Monis.

Mr Johnson has since been lauded for his heroism, after reports emerged that he tried to wrestle the shotgun away from Monis, sacrificing his life and allowing several of his fellow hostages to escape before police moved in.

His partner of 14 years, Thomas Zinn, and father, Ken Johnson, helped to carry the white coffin into St Stephen's Uniting Church for the service.

Ms Dawson's memorial was scheduled for later today.

Volunteers, meanwhile, removed thousands of bouquets of flowers mourners have left near the cafe over the past week, ahead of predicted rainy weather.

The flowers will be turned into mulch that officials hope to use at a permanent memorial site, while cards and letters left to honour Mr Johnson and Ms Dawson will be preserved in memory books for their families.

The permanent memorial will be set up after officials consult with the families, New South Wales Premier Mike Baird said.

Later, Prime Minister Tony Abbott joined hundreds of mourners at the University of Sydney for a memorial service honouring Ms Dawson, a highly respected lawyer and mother of three young children.

Her friend and fellow hostage Julie Taylor, who is pregnant, said Ms Dawson made her want to be a mother.

"Katrina's greatest love was the love for her family," Ms Taylor said.

"If there is one thing above all that we can learn from Katrina's example, it's how to love, to show love, to use love and by loving to make other people and places better."

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