Dog-walking app Wag has been accused of trying to silence a couple whose dog died in the care of one of their dog walkers.

Sara and Nick Moore, from Houston, Texas, say Wag offered them financial compensation in return for signing a non-disclosure agreement.

Winnie, a wheaten terrier, was hit by a car on a walk arranged through the app.

The company says it is "deeply saddened by what happened".

The couple used the "ASAP" feature of the app, which allows pet-owners to "order" a dog walker to arrive within the hour.

Mr Moore wrote on Facebook they had suspected something was wrong after not receiving the usual notification Winnie's walk was complete.

"When Sara called the walker, the walker answered and assured Sara that Winnie was home safe," he wrote.

"Five minutes later, Sara received a call from a Wag representative saying that Winnie was not home safe but had been hit and did not survive."

The couple were told by a Wag representative the company would "take care of all of the expenses, such as Winnie's cremation".

The company then issued the couple a non-disclosure agreement forbidding them from speaking about the incident.

"We could not leave any negative reviews. We could not make posts on social media. We could not hold Wag or the walker responsible," Mr Moore wrote.

He told BBC News the lack of information they had received about the circumstances of Winnie's death "makes the healing process very difficult".

The record of Winnie's last walk was deleted from the app and the couple still do not know where the accident was.

"When you don't know what happened, your mind fills the empty space with worst case scenarios that play over and over," Mr Moore said.

"Its been a terrible experience and we are both still going through it."

A Wag spokesman told the BBC: "As a company of dog lovers and pet parents, we're deeply saddened about what happened to Winnie.

"The walker, along with a good Samaritan, took the dog to a nearby veterinarian immediately after the accident.

"The walker has been deactivated from the Wag platform.

"We use a robust vetting process that includes an application and verification process, a third-party background check, and online tests covering dog safety and handling knowledge that each applicant must pass to be approved to work on our platform."

Mr Moore said they had had positive experiences with the dog-walking app previously.

"We made a lot of great relationships through our use of Wag and it allowed our sweet Winnie to be cared for while we maintained busy lifestyles," he said.

This is not the first time Wag has been in the spotlight over the behaviour of its walkers.

In 2018, the company came under fire after footage showing a Wag dog walker repeatedly hitting a dog was posted online.

Wag has been endorsed by a number of celebrities on social media, including Kendall Jenner, and in 2018 received $300m (£229m) in investment from Saudi Arabia.