A Ministry of Defence shooting range was forced to suspend a live firing drill after a group of suspected migrants landed a boat inside a restricted area and ran onto the site.
A reservist unit of British soldiers was shooting at Lydd Ranges, near Dungeness, when a spotter saw a powerful speedboat heading towards shore, having crossed the Channel early on Wednesday morning.
A "check fire" was called, but the boat made landfall inside the designated "danger area" and a group of 16 people ran inland.
Police and immigration officials were called to the scene and it is understood that all the migrants were located shortly after.
Lydd Ranges have been used for military training for over 150 years with a "danger area" extending out to sea. Red flags are flown in periods of live firing and were on display on Wednesday morning.
The landing will raise serious questions for Home Office officials because the boat on which the group travelled was fitted with a 300bhp engine which costs £20,000 on its own.
The rigid-hull inflatable boat (Rhib) the group travelled on is nine metres long and fitted with fixed seats, making it one of the most high spec vessels to have transported migrants across the Channel.
On board, it is understood that an Albanian passport was found among the discarded life jackets.
Smuggling gangs from Albania have been identified as facilitating the illegal crossings in recent months after lorry traffic slowed down because of the coronavirus pandemic.
In May, an Albanian people smuggler who helped to bring people into the UK on dinghies was jailed for nine years.
Vladimir Bardoshi, 36, led a gang that ferried illegal migrants across the Channel from France in dangerous conditions, police said.
Two accomplices were jailed in 2018, but police were unable to locate Bardoshi until he was found to be living in Spain in January.
He was extradited to the UK and pleaded guilty at Canterbury Crown Court.
Feim Vata and Xhemal Baco, who both pleaded guilty in November 2018, were arrested a month earlier while driving a vehicle carrying six Albanian migrants away from a Kent beach.
Baco had piloted a dinghy across the Channel, while Vata waited near the shoreline near Deal.
Police said Bardoshi was responsible for coordinating the operation, which made at least three trips from France.
More migrants crossed the Channel and arrived in Britain in September than in the whole of last year.
Nearly 2,000 people made it to the UK compared to 1,800 in 2019.
So far this year, around 7,100 people have made the dangerous journey across the world's busiest shipping lane.
In an interview with The Telegraph, Dan O'Mahoney, the Clandestine Channel Threat Commander, revealed UK authorities were "very close" to being able to deploy a new "safe return tactic" under which personnel would render individual boats inoperable by firing nets at their outboard motors and then use British vessels to transfer migrants back to France.
However France is currently refusing to accept such migrants back into the country-delaying the use of the tactic.
The Home Office has faced pressure to act after criticism of their approach to processing people who land in Britain.
Priti Patel asked Home Office officials to explore sending asylum seekers to islands in the south Atlantic, while others explored using offshore oil platforms, disused ferries and retired cruise ships.
Damian Collins, the Conservative MP for Folkestone and Hythe told the Telegraph: "It looks like a very nasty accident was avoided in Lydd.
"The scourge of human traffickers has for too long disrupted the lives of both my constituents, and of the asylum seekers whose lives they put at risk, extorting thousands of pounds out of them to then bundle them onto unsafe craft to cross the world's busiest shipping lane.
"I welcome the Home Secretary's commitment to bring forward new legislation that will deliver safe routes to the UK for those in genuine need, faster processing of claims, and accelerating removals for those whose applications have failed - helping those with legitimate claims, whilst clamping down on human trafficking gangs."
The Home Office has been contacted for comment.