The UK government confirmed Wednesday it has detained an unspecified number of migrants in recent days who are set to be deported to Rwanda in July under its controversial new policy.

It comes a week after lawmakers ended months of parliamentary wrangling and passed a contentious law allowing some asylum seekers to be deported by declaring Rwanda to be a safe third country.

Prime Minister Rishi Sunak, who has vowed to stop migrants arriving on small boats from mainland Europe, vowed last week to begin detaining people promptly before deportation flights start within "10 to 12 weeks".

Reports of immigration enforcement officers holding people earmarked for the flights emerged earlier this week. On Wednesday, the interior ministry confirmed that "a series of nationwide operations" were underway.

"The first illegal migrants set to be removed to Rwanda have now been detained," it added.

Calling it "another major milestone" in the Rwanda plan, the ministry released photographs and a video of immigration enforcement officers detaining several migrants at different residences.

They were seen being led away in handcuffs and put into secure vehicles.

Interior minister James Cleverly said they were "working at pace to swiftly detain those who have no right to be here so we can get flights off the ground".

A senior minister revealed Tuesday the government expects to deport 5,700 migrants to Rwanda this year, after the interior ministry confirmed that Kigali had "in principle" agreed to accept that number.

Of those, 2,143 "can be located for detention" before being flown there, the ministry said, leaving more than 3,500 currently accounted for.

Ministers have insisted the enforcement teams will find them.

The government has increased detention capacity to more than 2,200 spaces ahead of the first Rwanda flights, it said Wednesday.

Commercial charter planes have also been booked and an airport has been put on standby, it added.

On Tuesday, London confirmed that the first failed asylum seeker had travelled to Rwanda under a separate voluntary scheme.

Rwanda, home to 13 million people in Africa's Great Lakes region, lays claim to being one of the most stable countries on the continent and has drawn praise for its modern infrastructure.

But rights groups accuse veteran President Paul Kagame of ruling in a climate of fear, stifling dissent and free speech.

Sunak's ruling Tories argue the threat of being deported there will deter tens of thousands of annual cross-Channel arrivals, and insist the policy is already having an impact.

But official statistics show arrivals have increased by more than a quarter in the first third of the year compared to the same period in 2023.