Chinese courier giant ZTO Express came under fire after one of its business outlets in Chengdu, Sichuan province, was found to have transported puppies and kittens as part of the controversial pet blind box sales on e-commerce sites, China Daily reports.

In a statement late on Tuesday, ZTO apologized for collecting live animals from e-retailers for shipment, which it said breached rules.

The New York listed firm said it has shut the outlet in question for rectification.

A worker overseeing safety affairs in the province has also been suspended from work with the year's performance-based salary deducted, it added.

"The healthy development of courier companies is reliant on the strict application of industrial standards and safety management, as well as a proper value toward life," the statement said.

The pet blind box has been trending on multiple e-commerce platforms, including Taobao and Pinduoduo.

It allows users to buy pets of unknown breeds and appearances for about 10 yuan (US$1.50) or even lower.

Many such purchases involve a dayslong cross-provincial shipping process and has led to animals suffocating or dying of dehydration.

The hashtag "pet blind box" got more than 380 million views and about 100,000 comments on microblogging service Weibo by Wednesday.

Many users accused the business of cruelty and called for harsh punishments for all parties involved.

"Both the sellers and buyers are bad to the core," a Weibo user named Muxiyan Crystal commented.

China Central Television, the State broadcaster, weighed in on Monday, calling the business a "departure from humanity.''

"Relevant rules have forbidden the sending of live animals via postal services, and courier companies shall not violate the rules knowingly," it said on its Weibo account.

The online crusade came after volunteers from Chengdu Aizhijia Animal Rescue Center, a local animal welfare group, late on Monday intercepted about 160 packages containing such pets at the ZTO outlet.

Videos posted on the group's Weibo account showed cube cages muffled with braided cloth being stacked into a truck as a group of volunteers stormed the site, demanding the drivers unload the animals. Puppies could be heard barking in distress.

The group said it has taken control of the animals following health checkups organized by local animal disease control authorities.

A volunteer who asked not to be named for fear of retribution from sellers said four dogs and cats were found dead, and more than a dozen were diagnosed with diseases including distemper and cat plague.

She said her colleagues had prepared for Monday's operation for about two weeks and had successfully shone a spotlight on the practice, which she said masquerades as pet adoption projects on Taobao, Pinduoduo and Xianyu, a secondhand e-commerce site owned by Alibaba, she lamented.

"The business is everywhere," she said. "My colleagues and I have kept sending inquiries to customer service personnel of such shops, and many said they can still send out pets using courier services."

About 160 packages of pets, called 'blind boxes,' or gift boxes containing a surprise toy, shipped by ZTO Express.

Rescued from misery.

ZTO Express under fire for moving 160 packages of 'gift' pets sold online