Jacinda Ardern has said her cabinet is “completely unified” in reforming gun legislation in the wake of the Christchurch terror attack but emerged from a meeting with ministers without concrete proposals to change firearms laws.

The New Zealand prime minister had been expected to announce measures such as a ban on semi-automatic rifles, a plan that was flagged by her attorney general, David Parker, one day after the massacre in which 50 people died.

However, after emerging from a long cabinet meeting Ardern said her team would take the rest of the week to work out the details after agreeing to make changes “in principle”. The agreement had been reached just 72 hours after the attack, she said, comparing her response time to that of the Australian government after the Port Arthur massacre.

“Within 10 days of this horrific act of terrorism we will have announced reforms which will, I believe, make our community safer,” Ardern said at news conference.

New Zealand mosque attack: alleged gunman bought four firearms online – live Read more

“These aren’t simple areas of law. So that’s simply what we’ll be taking the time to get right,” she said.

Hours before Ardern’s appearance, the country’s biggest online auction site, TradeMe, banned semi-automatics and “associated” accessories, saying “it is clear public sentiment has changed”.

On Monday, an 18-year-old man was charged with distributing a live stream of the mass shooting and was denied bail. He reportedly posted a photograph of one of the mosques attacked with the message “target acquired” among other chat messages “inciting extreme violence”, the New Zealand Herald reported. His name has been suppressed and he is due back in court next month.

Previous efforts to change gun laws failed in 2005, 2012 and 2017. Deputy prime minister Winston Peters, whose NZ First party has previously not supported recommendations to restrict gun laws, said on Monday that, after Friday’s attacks: “Our world changed forever and so will some of our laws.”

On Monday, Ardern also said an inquiry would be launched into the events leading up to the shootings, including the suspect’s travel and social media use and whether concerns voiced by Muslim citizens had been taken seriously.

She urged gun owners to hand in their weapons, and advised anyone considering buying a gun to wait a few days to get some certainty around the laws before investing.

Play Video 1:36 Gun shop owner confirms accused Christchurch suspect bought from his business – video

Earlier, David Tipple, the managing director of retailer Gun City, confirmed his company had sold the suspect four weapons – but the gun he used to carry out the mosque shootings was not one of them. Tipple would not be drawn on his views on gun control, but intimated guns were not the issue.

“I had my grandson say to me: ‘Granddad, why do people think the guns were the problem? The guy was crazy.’ He is six years old,” Tipple told a media conference.

Earlier on Monday, TradeMe banned the sale of all semi-automatic weapons and “associated” accessories. Its CEO, Jon Macdonald, said the ban would be reviewed once there was more clarity on future gun laws.

He said: “We’ve had a lot of contact from Kiwis over the weekend about this issue, and many felt that we should stop the sale of these items in the wake of this attack. We’ve listened to these sentiments and we’ve put this ban in place while we await clear direction from the government.”

The focus fell on semi-automatic military-style rifles with high-capacity magazines at the weekend after Ardern said it was believed the weapons used in the attack had been modified and that loopholes that allow such modifications would be closed.

Gun control experts told the Guardian such weapons can be easily converted into a military-style semi-automatic rifle using a high-capacity magazine, the sale of which is not regulated in New Zealand.

Grieving, exhausted, Christchurch tentatively returns to work after massacre Read more

The attorney general said such rifles would be banned after it emerged the suspect in Friday’s attack used five guns, two of which were semi-automatics.

Police commissioner Mike Bush has urged locals to return to their normal lives, to remain “vigilant” but to reject fear and reclaim the streets of their city.

But on Monday it was hard for residents to embrace routine and normality as diggers fanned out around the city to prepare 50 graves. Experts in Islamic burial rights also converged on the city.

Raf Manji, a Christchurch city councillor and a Muslim, told Nine to Noon: “There’s a sense of weariness. It’s been a very long, hard weekend, and I think people will be a little bit washed out and will be pleased to be back in their places of work and study, and congregate with their friends and colleagues.

“People coming together will be a good thing for the city … this is an attack on the whole community, we talk about the Muslim community but they’re just part of us, they’re part of our normal everyday life. The way the public has come out here shows the community is rejecting what has happened to it.”

Reactions differed in the wake of the attack, at Christchurch firearms retailer Gun City panic-buying began. One customer, Rick, said on Sunday afternoon there was no reason for anyone to buy a semi-automatic besides “looking cool”. “They are far too strong for hunters, they will rip any animal to shreds,” said Rick, who hunts deer.

Reports emerged of others choosing to hand in their firearms after Friday’s events.

Blackstone (@SirWB) Since I first heard about the atrocity on Friday afternoon I have reflected and reserved my thoughts.

Monday morning - this is one of the easiest decisions I have ever made.

Have owned a firearm for 31 years. pic.twitter.com/fBFqfd0gTm

Simon Bridges, the leader of the opposition National party, said he understood gun laws needed to change, and his party would work “constructively” with the government to fast-track tighter controls, with a ban on semi-automatics “probably the right way to go”.

“I am open to any and all changes,” said Bridges to Radio NZ.

The Police Association too said it fully supported such plans. Its president, Chris Cahill, said: “Jacinda Ardern has said emphatically that New Zealand’s gun laws will change … I absolutely agree with her. It is sickening that it has taken this horrific event to wake us up to our vulnerability.”

Civilians in New Zealand own an estimated 1.2m firearms, according to the 2017 small arms survey. That makes New Zealand’s per capita rate of gun ownership higher than Australia’s, but still far below the US, where there is more than one gun per person.

The country’s gun laws are largely unchanged since 1992, when controls were tightened after the 1990 Aramoana massacre, in which a man killed 13 people with a semi-automatic rifle.