Thousands of travellers waited in hours-long queues at US airports on Sunday due to increased spring travel and limited security personnel who have been working without pay during a partial US government shutdown.

Photos show people standing in long queues at check points managed by the Department of Homeland Security (DHS) at airports in Houston and New Orleans.

The DHS has gone without funding since 14 February after Congress failed to reach an agreement. The Trump administration blamed delays on Democrats, who declined to pass funding without immigration reforms.

The delays come during a busy travel season as US students have their spring holidays from school.

Officers with the DHS' Transportation Security Administration (TSA) must keep working because they are considered essential workers for public safety, even though there is no money to pay them. It is likely they will receive back pay after the shutdown.

Queues at Louis Armstrong International Airport outside New Orleans stretched into the airport's car park on Sunday, as travellers took to social media to complain.

The airport said on social media that a shortage of workers was causing the delays and advised travellers to arrive "at least three hours" before their scheduled departure.

Ben Brasch and a friend were among those in the queue in New Orleans. They had been queuing up for 15 minutes, still in the car park, nola.com reported.

"I hope we make our flight," he told the local news site. "But I feel bad for the [airport] workers having to deal with this."

At William P Hobby Airport in Houston, waiting times at security check points could exceed three hours, the airport warned on social media. It advised travellers to arrive four or five hours before their flights.

Videos and photos of the lengthy lines flooded social media on Sunday. The DHS said "Americans are now enduring the severe fallout from the Democrat shutdown".

The clogging of checkpoints at two major airports in the US offered a preview of what could await travellers at others in the coming weeks as the shutdown continues.

TSA employees have received partial paycheques since the funding ran out, but could go without pay if the shutdown continues.

"Democrats are shamelessly playing politics with national security, punishing hardworking TSA workers and their families," Lauren Bis, the deputy assistant secretary for public affairs at the DHS.

Going without paycheques has led to "financial hardship, absences and crippling staffing shortages", Bis said.

The partial shutdown began three weeks ago when Democrats refused to fund the DHS without more restrictions on US Immigration and Customs Enforcement (ICE), another agency that falls under the department's jurisdiction.

ICE will not be significantly affected by the shutdown because of Congress already provided the agency funding.

But Democrats have been demanding reforms to the agency as part of any funding deal after federal agents killed two Minneapolis residents, Alex Pretti and Renee Good, who were protesting against the Trump administration's immigration raids in Minnesota in January.

They have asked that the DHS bar immigration agents from wearing face masks, provide better identification for officers and tighten rules for obtaining warrants.

Repeated votes on measures to fund the DHS have proved unsuccessful so far.

On Sunday, Washington Senator Patty Murray said Democrats are holding out for changes.

"Democrats want to get TSA agents paid, but we won't help Republicans cut a blank check" that allows continued, unchecked immigration enforcement crackdowns, Murray said.