Human rights activist Van Kham Chau, 70, was arrested in Ho Chi Minh City in January during a meeting with a Brotherhood for Democracy campaigner, while on a "fact-finding" mission to Vietnam.

"On July 29, 2019, investigation agencies issued the decision to prosecute Chau Van Kham and accomplices for terrorist activities against the People's administration," Vietnam's press and information department said in a statement to the ABC on Thursday night.

The statement said this involved the alleged use of "forged documents of agencies and organisations".

Mr Chau is an active member of pro-democracy and human rights group Viet Tan, which the Vietnamese Government alleges is a terrorist organisation — a claim dismissed by Mr Chau's family, members of the organisation and international observers.

His son, Daniel Chau, told the ABC last month the idea that his father, a retired small businessman who came to Australia as a refugee after the Vietnam war, could be a terrorist was "ludicrous".

"My dad's in his 70s. He's passionate, but he alone isn't going to cause violence or anything like that," he said at the time.

Mr Chau was being investigated under Article 109, which refers to alleged operations to overthrow the Communist Government, and Vietnamese authorities have alleged Mr Chau entered Vietnam on false documents through the land border with Cambodia.

Article 109 says a person who joins an organisation that acts against the people's government can be punished with 12 to 20 years behind bars, life imprisonment or death.

When asked if the death penalty was being considered in Mr Chau's case if he were to be convicted, the ministry did not rule it out.

"As in other countries, in Vietnam, any infringement of the law is subject to strict punishments in accordance with the law," the ministry said.

The news of Mr Chau's impending trial comes as Human Rights Watch (HRW) called on the Australian Government to call out Vietnam's "abysmal human rights record", as Canberra hosted the 16th Australian-Vietnam human rights dialogue yesterday.

"The crackdown on basic rights in Vietnam is escalating, with more political prisoners being unjustly detained for longer terms," HRW Australia director Elaine Pearson said in a statement, adding at least 131 people were behind bars in Vietnam for exercising their basic rights.

"Australia should press Vietnam to change its rights-violating criminal procedure code so that all criminal detainees have prompt access to legal counsel as international law requires."

PM 'failed to address human rights concerns publicly'

Prime Minister Scott Morrison visited Vietnam last week in a bid to bolster trade relations.

He also issued a thinly veiled swipe about China's aggression in the South China Sea, which affects islands claimed by Vietnam.

But HRW said he "failed to address human rights concerns publicly during his visit" to Hanoi.

A spokesperson from the Department of Foreign Affairs and Trade (DFAT) told the ABC consular assistance was being provided to an Australian man detained in Vietnam but was unable to provide further details for privacy reasons.

Mr Morrison has been vocal about the case of Sydney academic Yang Hengjun, who has been detained since January in China.

On Thursday, Mr Morrison rubbished claims that Dr Yang had been working as a spy, saying espionage allegations were "absolutely untrue".

Vietnam's Foreign Ministry said Mr Chau had received eight consular visits and his conditions in custody — including being denied access to a lawyer until the investigation was complete — were in accordance with their laws.

"The period of detention and access to lawyers are to comply with regulations of the law," the statement said.

There was no mention of Mr Chau's case in a joint statement from Mr Morrison and his Vietnamese counterpart from August 23.

The statement referred to the countries as "strategic partners" with a "common outlook".

"The two countries will broaden bilateral security cooperation, including in the maritime and cyber domains, and work together to combat transnational crime in Vietnam and Australia, including through increased border security cooperation and law enforcement activities."

By Erin Handley - Ausralian Brodcasting Corporation News - August 30, 2019