Lawyers in the US have filed a petition seeking the release of an Afghan family detained in the US, despite having valid entry visas.

A couple and their three young children were taken into custody shortly after their arrival at Los Angeles International Airport last week.

They had Special Immigrant Visas, granted for work done for the US military that put their lives at risk.

Afghanistan was not among the countries listed on a now blocked US travel ban.

The original order prohibited the entry of immigrants from seven Muslim-majority countries, but has since been halted by US federal courts. The Trump administration is preparing a new executive order.

A petition for the release of the Afghan family was filed by the International Refugee Assistance Project, which said the family had been taken into custody "with absolutely no justification" and it was a violation of due process rights under the US constitution.

'Extremely unusual'

The man was detained in a maximum-security detention facility in Orange County, California, Becca Heller, the director of the International Refugee Assistance Project, told AP news agency on Sunday.

Though his wife and children - aged seven years, six years and eight months- were initially taken to a similar facility in Los Angeles, they were later moved to a hotel, she said.

The Special Immigrant Visas, created by Congress for citizens from Iraq and Afghanistan, can be granted to to those who have helped the US military as drivers, interpreters and in other jobs, which often put their lives at risk in those countries.

One of the lawyers defending the family said it was "extremely unusual if not entirely unique" for someone who holds this special visa to be detained upon arrival.

"The visas require extreme vetting to get," said Talia Inlender, a lawyer with the legal aid group Public Counsel.

The petition filed in US District Court in Santa Ana, California, south of Los Angeles, also said that US Customs and Border Protection (CBP) agents has held the family in isolation without access to legal counsel.

"Despite repeated requests, the CBP has provided no information regarding why the family was detained, whether they have been questioned, and whether any reason at all exists to justify their continued detention," the petition said.