The number of unlawful crossings by migrants at the US southern border has dropped for the fifth consecutive month, according to official data.

US Border Patrol agents apprehended around 57,000 migrants along the border in July - the lowest recorded since September 2020.

The numbers are down significantly from December when around 250,000 migrants were caught crossing the border.

President Joe Biden's administration has credited the decrease to recent actions by him to tackle illegal immigration into the US, an election-year political vulnerability for the Democrats.

"This is the product of a number of actions this administration has taken," said Homeland Security Secretary Alejandro Mayorkas in an interview with CBS this week.

Mr Mayorkas said those actions include an executive order signed last month by President Joe Biden that allows US immigration officials to deport migrants without processing their asylum claims.

The measure has been called one of the most restrictive border policies by a Democratic president in recent times, and was criticised by left-wing members of the party.

At the time, the president vowed that his executive order would "help us gain control of our border". He added that "doing nothing is not an option".

Government data shows that the number of migrants stopped at the US-Mexico border had dropped even before the order.

Border Patrol recorded 141,000 apprehensions in February, 137,000 in March, 129,000 in April, 118,000 in May and 84,000 in June.

The figures do not include official border crossings, where the Biden administration has been processing around 1,500 migrants each day through a smartphone app that schedules appointments between migrants and US border agents.

On the other side of the border, Mexican officials have also been working to curb illegal migration, including stopping people before they attempt to cross on to US soil.

The southern border has been a political headache for the Biden administration heading into November’s election.

Mr Biden has been repeatedly criticised by Republicans and their party’s presidential nominee, Donald Trump, who said last month that the president had “surrendered our southern border.”

The president hit back, accusing the Trump camp of an "extremely cynical political move" by pressing Republican politicians to block a proposed border plan in Congress earlier this year.