US President Donald Trump has threatened to disarm Hamas “violently” amid moves by the group to reassert control over the Gaza Strip, targeting what it called “collaborators”.

Speaking to reporters on Tuesday, Trump said if Hamas failed to disarm within “a reasonable period of time” then “we will disarm them”. He did not say when he expects the group to surrender its weapons.

His comments came as footage circulated online showing a public execution and other displays of force by Hamas fighters in Gaza since the US-brokered ceasefire began last week.

The execution – which BBC Verify geolocated to a junction in central Gaza City – follows Hamas’s pledge to crush “lawlessness” in the Strip.

Other verified clips have shown armed men wearing insignia identifying them as members of Hamas’s internal security force on patrol and masked fighters firing on unarmed men.

Analysts told BBC Verify that the show of force is at least partially intended to counter armed clans which have increasingly challenged the group’s hold on the Strip over the past two years.

Tensions between Hamas and some of the groups it is now fighting stretch back before the war. Some – like the Dughmush clan – have historically been involved in smuggling over the Strip’s border with Israel, an expert told BBC Verify. Recent clashes between Dughmush and Hamas left more than 50 people dead, including 12 Hamas members.

Israel has previously said it has supplied weapons to other armed groups in the Strip. One Hamas internal security unit recently pledged to “eradicate gangs and militias” it accused of co-operating “with the enemy”.

A clip which emerged on Monday afternoon showed Hamas fighters executing a group of eight men. BBC Verify geolocated the footage to a junction in the central Zeitoun neighbourhood in Gaza City, which had been the focus of a major Israeli ground offensive in recent weeks but is now back under Hamas control after the Israeli military withdrawal.

Fighters – some of whom were wearing body armour and Hamas headbands – could be seen in the footage lining the men up in front of a large crowd, which appeared to include at least one young child.

After forcing the men to their knees, crowds could be heard shouting “collaborator” or “agent”.

The assembled fighters then opened fire on the bound men, who fell to the ground. Afterwards, the men fired into the air and shouted “long live the al-Qassam Brigades” – Hamas’s military wing.

Another verified video showed masked and armed fighters forcing a man to his knees in the middle of the same Zeitoun junction before shooting him in the leg.

Several other gunshots also rang out, followed by screams, but the footage doesn’t show whether others were attacked. In the aftermath of the footage, several armed men stand guard around the injured man, waving away onlookers who witnessed the incident.

It is not clear what prompted the incident, which first emerged online on 10 October. Google image searches returned no earlier results.

Palestinians who spoke to the BBC expressed fear at the public executions.

“Why are people cheering for chaos? A masked man kills another masked man without any proof, without investigation, without a court, without even a waiting period for appeal what do we call this? Resistance? No, this is lawlessness,” a lawyer living in Gaza said.

“You can’t correct one mistake with another,” one activist living in central Gaza Strip added. “Executions without fair trial are a crime. May God guide our people .”

Meanwhile, members of Hamas’s internal security force have also been deployed across Gaza City in a show of force by the group.

Two such fighters, sporting the insignia of internal security units and armed with rifles, could be seen in several images geolocated by BBC Verify stationed at a crossroads in Gaza City.

Other shows of force included armed men wielding assault rifles marching through a market in the Zeitoun area followed by a small group waving a Palestinian flag.

“I think what Hamas has been trying to do is mobilise its forces, using its interior ministry forces, to assert and consolidate its control,” Professor Fawaz Gerges, Professor of International Relations at the London School of Economics, told the BBC’s Today Programme.

“In the areas where it’s Hamas control, Hamas will be able to destroy the various clans and gangs and looters and militias because its forces are more seasoned, more skilled, more determined,” he added.

While Hamas has long had simmering rivalries with various armed groups in the Strip, Israel’s bombardment of Gaza and the loosening of Hamas’s grip on power has allowed some of the clans to grow in strength, analysts say.

“The collapse of other social institutions has increased the appeal of the clan, which can serve as a social network for its members,” Yaniv Voller, a senior lecturer in Middle East Politics at the University of Kent, told BBC Verify.

“At least some of the clans have been reported to have received weapons and other support from the Israel Defense Forces (IDF), to serve as proxies against Hamas,” he added.

Some of the militias are also operating in IDF-controlled areas. By analysing videos circulating on social media, BBC Verify identified bases used by two rival groups deep inside IDF controlled territory, including one near the southern city of Rafah, and one ​​near the northern town of Beit Hanoun.

In response to Hamas’s re-emergence and the role of its security forces in policing, Trump previously said this did not fall outside the peace agreement.

“[Hamas] do want to stop the problems and they’ve been open about it, and we gave them approval for a period of time,” he told reporters on Monday.

“You have close to 2 million people going back to buildings that have been demolished, and a lot of bad things can happen. So we want it to be – we want it to be safe.”

Prof Gerges said that the US and its allies had little choice but to allow Hamas to exhibit some show of force in Gaza if the ceasefire was to have any meaningful impact.

“Without security you cannot deliver aid. Without security you cannot really have life,” he said. “The Americans realise that the only force is Hamas and that’s the irony.”

Additional reporting by Emma Pengelly and Ahmed Nour.