CHRISTCHURCH, New Zealand — Rescue crews switched off their jackhammers and joined in two minutes of silence observed across New Zealand on Tuesday to mourn as many as 240 people killed in an earthquake exactly one week earlier.

Church bells tolled throughout the country at 12:51 p.m. to mark the start of a national commemoration for those lost when the quake struck the southern city of Christchurch, collapsing office blocks and sending bricks and other rubble tumbling into the streets.

Thousands of people across the city gathered in groups, or on their own, paused and bowed their heads. Backhoes and bulldozers tugging at the massive piles of rubble rumbled into silence. Traffic simply stopped.

Flags flew at half-staff across the country, and Prime Minister John Key asked the nation's 4.5 million people to join in a show of unity for people "enduring tragedy beyond what most of us can imagine."

The bells pealed again to end the silence. People hugged in the streets, cars started and moved on, and crews picking through the rubble fired up their machines and went back to work.

Police said they have pulled 154 bodies from the wreckage, and said the number of others missing and feared dead indicated a final death toll higher than previously thought.

"The figure ... of around 240 is solidifying," Superintendent Dave Cliff told reporters.

The magnitude 6.3 quake struck within a few miles (kilometers) of downtown Christchurch, when the southern city of 350,000 was bustling with workers, shoppers and tourists going about their activities. It brought down or badly damaged office towers, churches and thousands of homes across the city in one of New Zealand's worst disasters.

More than 900 international urban disaster specialists are among hundreds more local officials who continued to pick through the wreckage Tuesday. No one has been pulled out alive since the day after the quake, and officials say it is almost certain no one else will be.

"Realistically it would be a miracle if we encountered anyone at this stage on any of the sites which we are currently working on," said Jim Steward-Black, the co-ordinator of the New Zealand urban search and rescue teams.

For Tuesday's ceremonies, people left offices, warehouses, factories and homes and stood in the street in silence.

At one of Christchurch's busiest intersections, traffic halted in the shadow of the Knox Church and the historic Carlton Hotel, both ruined in the quake.

"I was born here, I've lived here all my life and I'll die here. It's my home and it hurts so much to see it in this way," said Mike Cochrane, fighting back tears as he sat under a tree on the central traffic island.

The realtor's office where Rosie MacLean works is the only unbroken building on the four corners of the intersection.

"I suppose this is about hope, really, to realize we've got a future somewhere," she said of Tuesday's commemoration. "But that's just hard to find at the moment. I guess this means we've reached a point where we can all acknowledge it together, which is a beautiful thing."

At the headquarters of the rescue effort, bustling in the past week with the vivid urgency of its mission, work paused for the first time. Key, who grew up in Christchurch, joined the ceremony there, clutching the hand of his wife, Bronagh, who was born in the city.

On Monday, a 5-month-old boy who was the youngest known victim of the disaster was its first laid to rest. A second funeral, for 22-year-old local Jaime Gilbert, was held Tuesday. With only six other people publicly identified so far, most other funerals may be some time off.