A Myanmar court sentenced a female activist to six months in jail on Monday for a Facebook post satirising the powerful military, the latest crackdown against free speech in the former junta-ruled country.

Freedoms have flourished since the junta ceded full control to a partly civilian government in 2011, culminating in landmark elections last month.

But there have been growing concerns over renewed breaches of civil liberties. Criticism of the still powerful military remains fraught with risk.

Chaw Sandi Tun, 25, was arrested in October after a post on her Facebook page made fun of the army.

"My daughter was sentenced to six months' imprisonment at Ma U Bin township court this morning under Section 66(d) of the telecoms law. We will appeal as we are not satisfied," her mother Ei San told AFP.

She was referring to a broadly worded law which bans the defamation or "disturbing" of people through any telecommunications network.

The maximum penalty she faced was three years in jail.

Her lawyer confirmed the sentence but said his client denied making the post.

"She said her Facebook account had been hacked several times and that she didn't post that post," Robert San Aung told AFP.

The post compared the colour of a new uniform for army officers with that of a "longyi" (traditional skirt) worn by National League for Democracy (NLD) leader Aung San Suu Kyi, whose party swept last moth's polls and will form a government next year.

"If you love mother that much, why don't you wrap mother's longyi on your head?" the post said.

The United States embassy has previously called for the release of Chaw Sandi Tun and Patrick Khum Jaa Lee, another activist who has been arrested over Facebook posts critical of the military.

Myanmar has come a long way since the decades of brutal rule under a junta which tolerated little dissent, jailed critics, ran vast informant networks and kept the nation closed off as its economy collapsed.

The quasi-civilian government which replaced outright junta rule in 2011 was widely praised for a series of political and economic reforms, with most international sanctions dropped.

In recent years social media has also exploded, a new phenomenon in a country where owning a mobile phone just five years ago cost thousands of dollars.

But in recent months the military and its incumbent army-backed government have been accused by rights groups of returning to junta-era tactics. There was widespread criticism of a violent police crackdown on student protesters earlier this year.

In February a freelance photojournalist was arrested for uploading a satirical post on Facebook mocking the military.

And in October 2014 another freelance journalist was shot dead by the army in a case raised by US President Barack Obama during his official visit to Myanmar.

Two soldiers were later acquitted of the murder in a country where the powerful military remains shielded from civilian oversight.