Golden Dawn leader Nikos Mihaloliakos remanded in custody
The head of Greece's far-right Golden Dawn party, Nikos Mihaloliakos, has been remanded in custody on charges of organising a criminal group.
He appeared before investigating magistrates at an Athens court in a hearing that lasted into the early hours of Thursday.
He was one of six MPs arrested at the weekend amid outrage over the murder of an anti-racist musician.
Three have been freed pending trial while a fourth was remanded in custody.
All four have denied the charges against them.
The fact that three were freed pending trial will raise questions over how watertight the government's case against them actually is, the BBC's Mark Lowen reports from the Greek capital.
In all, 22 people were detained following the 18 September murder of Pavlos Fyssas.
A man held for the stabbing told police he was a Golden Dawn supporter, though the party strongly denies any link.
Mr Mihaloliakos faces charges including murder, assault and money-laundering.
He again denied the charges during his latest court hearing, the website of Greek newspaper Ekathimerini reported.
He said he condemned the murder of the musician but insisted "I am not a Nazi", the paper said.
Mr Mihaloliakos has been remanded in custody pending his full trial, which the authorities are keen to conclude swiftly.
Earlier, prosecutors found there was insufficient evidence to keep three of the MPs in detention.
MP and party spokesman Ilias Kasidiaris was freed on Wednesday on bail of 50,000 euros (£42,000; $68,000) and banned from leaving the country.
On leaving the court, Kasidiaris was filmed punching a video camera as he and his co-defendants barged journalists aside.
Fellow MPs Ilias Panagiotaros and Nikos Michos were freed under travel bans but with no bail set. They too left court in a belligerent mood, insulting reporters as "losers" and "little slaves".
A fourth MP, Yannis Lagos, was remanded in custody.
The plea session lasted 18 hours, Reuters news agency reports.
Mr Mihaloliakos's deputy, Christos Pappas, is set to appear in court in the coming days.
Any MPs finally convicted would lose their seats in parliament, prompting by-elections and - the government hopes - leading to the destruction of Greece's neo-Nazi party, our correspondent says.
During Tuesday's court appearances, there was a heavy presence of riot police - a reminder that despite falling popularity in the opinion polls, the party still commands significant support, our correspondent says.
Supporters outside court chanted slogans, including: "You are heroes!"
Details from witness testimony have been emerging about the way in which the party operated.
The testimony speaks of a strict hierarchical structure - or "Fuehrer principle" as the indictment calls it - as well as assault squads and military-style training, our correspondent says.
Searches of the homes of some MPs have found Nazi paraphernalia as well as unlicensed weapons, ammunition and bundles of cash.
The government is hoping that lurid witness testimony that has emerged - for example, of thugs hired by Golden Dawn to go through Athens on motorbikes assaulting immigrants - will permanently wreck the party's image, our correspondent says.
The crackdown was sparked by outrage at the murder of Fyssas, 34, an anti-racist rapper known as Killah P.
George Roupakias, 45, who said he was a supporter of Golden Dawn, was arrested in connection with the killing.
On Friday, Golden Dawn - which won nearly 7% of the vote in 2012 elections - threatened to pull its 18 MPs out of the 300-strong parliament.
The governing coalition headed by Prime Minister Antonis Samaras, which has 155 seats, would then face by-elections.
Speaking on a visit to the US on Monday, Mr Samaras vowed to eradicate the "shame of neo-Nazism".
In recent months, Golden Dawn has been accused of perpetrating attacks on migrants and political opponents.
Golden Dawn officially denies being a neo-Nazi movement, despite its swastika-like insignia.