Cheng, 48, was a business television anchor for Chinese state television when she was detained in August 2020 for allegedly sharing state secrets with another country.

Cheng, who was tried in secret in March 2022, arrived in Melbourne and has been reunited with her two children and family, Albanese told a press conference.

"Tight hugs, teary screams, holding my kids in the spring sunshine. Trees shimmy from the breeze. I can see the entirety of the sky now! Thank you Aussies," Cheng wrote on social media.

Albanese said his government had been seeking for Cheng to be reunited with her children "for a long period of time and her return will be warmly welcomed not just by her family and friends but by all Australians".

Her release follows the completion of legal processes in China, he said.

China's State Security Ministry, for the first time giving details of the charges against Cheng, said she had pleaded guilty to charges of illegally sending state secrets abroad related to her work for a state media outlet. She had been deported after serving her sentence of two years and 11 months.

Australian diplomats were refused entry to her trial and Cheng has never publicly commented on the case.

Australia had repeatedly raised concerns about her detention, which came as China widened blocks on Australian exports amid a diplomatic dispute that is gradually easing.

"She is a very strong and resilient person," said Albanese, who said he has spoken to Cheng and welcomed her home on behalf of the country.

In a letter to Australia released publicly in August, Cheng wrote of missing her children aged 11 and 14, who have been living in Melbourne with their grandmother while she was detained.

"In my cell, the sunlight shines through the window but I can stand in it for only 10 hours a year," she wrote in what she called a "love letter to 25 million people".

Albanese, who came to power last year with a goal of improving relations with Australia's biggest trade partner, said he expected to visit China this year.

There had been public pressure on Albanese to secure Cheng's release before any official visit to China.

'PROGRESS'

Albanese had previously said he raised Cheng's case with Chinese President Xi Jinping.

Analysts said the release was a breakthrough but differences remained.

"This is one of the more concrete signs that Australia is no longer being punished by China for comments and policy measures that Beijing had objected to," said Ryan Neelam, analyst at the Lowy Institute think tank.

"So this does seem to suggest there is real progress ... But it doesn't completely change the overall structural difficulties that have been present."

Albanese said Australia "continued to advocate" for another detained Australian journalist, Yang Hengjun, who has been held since January 2019.

There has been no sign that Yang would be released and his situation remained grim, a close friend of the blogger told reporters on Wednesday. A verdict in his national security trial has been repeatedly delayed.

Cheng's jail sentence was relatively light for the charge of leaking state secrets, said David Zhang, a Beijing-based lawyer with Mo Shaoping Law Firm.

James Laurenceson, director of the Australia-China Relations Institute at the University of Technology Sydney, said Beijing was sending a "clear signal" with the release that it wanted the visit to China by Albanese to be a success.

"When the Albanese government came to power, the problems were in three baskets – no senior political dialogue, trade disruptions and the detained Australians. We’ve now had progress across the board," Laurenceson said.

China's ambassador to Australia said it was necessary to maintain the momentum of stability and improvement in relations, adding that China regarded Australia as a friend, and Australia had no reason to regard China as a threat.

China has previously detained foreign nationals on national security charges only to release them with little explanation.

Those include two Canadians who were detained for more than three years on espionage charges and released in September 2021 hours after Huawei Technologies executive Meng Wanzhou reached a deal with U.S. prosecutors to end a bank fraud case against her.

Beijing denied their arrests were linked.

The State Security Ministry said Cheng had "voluntarily pleaded guilty and accepted the punishment".

"In May 2020, Cheng Lei was solicited by someone from a foreign organisation and, in violation of the confidentiality clause signed with her employer, illegally provided state secrets obtained in the course of her work to the foreign organisation through her mobile phone," it said.

Judicial authorities tried the case in accordance with the law and fully guaranteed her rights, it said.