The victims of the MH17 disaster have been remembered at a service at St Patrick’s Cathedral, the focus of a national day of mourning.

MH17 victims represented the best of modern-day Australia and will never be forgotten, the prime minister has told mourners at a national memorial service.

One thousand mourners gathered at St Patrick’s Cathedral in Melbourne to remember the 38 Australian citizens and residents who were killed on July 17 when the Malaysia Airlines jetliner was downed by a missile over eastern Ukraine. All 298 people on board perished in the disaster.

“You have not been abandoned and you never will be,” Prime Minister Tony Abbott told the congregation, which included many family and friends of the victims.

He said it was a time to rededicate the nation to supporting the bereaved, obtaining justice for the dead and for their families, and to working for a better world.

“The dead of flight MH17 reflect what’s best in modern Australia: doctors who worked with refugees, teachers who worked with indigenous people and children with disabilities, volunteers in our armed forces and with local charities, business innovators and pillars of local communities, young people filled with passion for the life before them,” he said.

Hundreds of Australian police and defence personnel have been working with their Dutch and Malaysian counterparts in eastern Ukraine to collect human remains and evidence.

But their work has been suspended due to increased fighting between Ukrainian military and pro-Russia separatists.

“We try to create order in the midst of chaos and we try to inject decency into the vilest of situations,” Mr Abbott said of the mission.

Mourners shed tears as they placed yellow wattleseed branches on a wreath to remember the dead.

Amid the pipe organ and gothic columns, singers Katie Noonan and Abby Dobson injected a modern element singing the Leonardo’s Bride song Even When I’m Sleeping.

Catholic Archbishop of Melbourne Denis Hart welcomed the congregation before the Australian Boys Choir sang the national anthem.

Archbishop Hart said the attack was worthy of condemnation.

“The why of terror, the incredulity and condemnation of the perpetrators gave way to an avalanche of compassion, love and prayer for those so burdened,” he said.

“Here in Melbourne today, regardless of origin or creed, we stand in solidarity with those who are suffering unimaginable loss.”

Leaders of different faiths addressed the packed cathedral before Governor-General Sir Peter Cosgrove spoke of the grief, shock, anger, confusion and loss felt across the globe as a result of the disaster.

“So often words do not and cannot express our true feelings and thoughts during such a time of great loss,” he said.

He paid tribute to the West Australian Maslin family, who lost children Mo, Evie and Otis – aged 12, 10 and 8 respectively – along with their grandfather Nick Norris.

“In spite of the enormity of their loss, the depth of their despair, their love exceeds and surmounts all the hatred in the world.”

Opposition Leader Bill Shorten said the nation was united in its grief.

“We mourn 38 of our own who laughed, learned and loved beneath the Southern Cross that today flies at half mast around the nation,” he said.

The Victorian capital, cloaked in sombre grey skies on Thursday morning, was chosen because 16 of the 38 Australian citizens and residents killed were from that state.