BANGKOK (AFP) - The European Union has voiced "extreme concern" about political detentions and censorship in Thailand, as the military junta chief met officials and began to set out plans for the country's future.

The EU - a key trade partner of the South-east Asian nation - said only a clear plan for the country's return to democracy could allow its "continuous support" after the Thai military seized power last week and set about rounding up political figures, academics and activists.

"We are following current developments with extreme concern," the EU foreign affairs head Catherine Ashton said in a statement.

"We urge the military leadership to free all those who have been detained for political reasons in recent days and to remove censorship," she added.

The junta on Thursday added nearly 50 more names to the upwards of 250 people it has summoned, having held scores of people without charge at secret locations for up to a week.

Authorities have curtailed civil liberties under martial law and imposed a nightly curfew.

A week after seizing power, Thailand's coup leader, General Prayut Chan-O-Cha, met central and regional officials and laid out three stages that he envisioned for the country before it could be returned to democratic rule, without giving a timeframe.

The country would stay under "special law" during the first phase and then later set up a national assembly and "reform council", according to army spokesman Sirichan Ngathong.

Only then would the country start the process of preparing for elections, she said.

Thailand has seen 19 actual or attempted coups since 1932.

The regime freed some 30 people, including Niwattumrong Boonsongpaisan, who was caretaker premier at the time of the coup, on Thursday - a day after releasing leaders of the "Red Shirt" movement allied to the ousted government.

It has instructed all those set free to refrain from discussing politics under threat of prosecution in a military court.

Senior members of their rival protest movement as well as former premiers Yingluck Shinawatra and Abhisit Vejjajiva have also been held and since released.

A fugitive former cabinet minister arrested by soldiers who swooped on a press briefing a day earlier was brought before a military court on Wednesday to acknowledge charges of denying an order to report to the junta, and of "provocation", police said.

If convicted, ex-education minister Chaturon Chaisang could be imprisoned. He had used a press conference to criticise the coup minutes before being detained.

ARMY DENIES FACEBOOK BLOCK

Following a threat of a crackdown on social media, Facebook users on Wednesday reacted with alarm to rumours of a "block" of the popular site.

After an outcry on the Internet, the army interrupted national television to deny it had blocked Facebook after the site briefly went down.

But the military has warned against small but persistent daily anti-coup protests, mainly in the capital Bangkok.

Army spokesman Winthai Suvaree said authorities should prosecute demonstrators and could use teargas against the rallies, although he added they would "avoid violence".

The current political turmoil centres on the divisive figure of Thaksin Shinawatra, Yingluck's older brother, who was deposed as prime minister by royalist generals in a 2006 coup and now lives in self-imposed exile to avoid prison for a corruption conviction.

His opponents in the establishment, military and among the Bangkok middle classes view the entire Shinawatra family as corrupt.

Anti-Shinawatra protesters staged nearly seven months of protests before the May 22 coup in an attempt to rid the country of the family's influence.

At least 28 people have died in related violence.

Thaksin, a billionaire tycoon-turned-politician, has broad support among the urban working class and rural communities in the north and north-east, particularly for popular policies including providing nearly free health care.

He or his allies have won every election in the country since 2001.

Thailand has been rocked by increasingly severe political division and street protests since he was deposed in 2006.

More than 90 people were killed and hundreds injured during Red Shirt protests in 2010 that ended with a crackdown by soldiers firing live rounds.