The authorities in Bulgaria have arrested a local Roma leader on charges of threatening to commit murder.
The detention of Kiril Rashkov - nicknamed "King Kiro" - comes amid heightened ethnic tension in Bulgaria.
Anti-Roma demonstrations have spread and turned into the worst violence for years, leading to mass arrests.
The unrest began on Saturday after a van carrying members of Mr Rashkov's family ran over and killed a 19-year-old man in a southern village.
An angry crowd of about 2,000 people then gathered and attacked three houses owned by the Roma leader in the village of Katunitsa, shouting anti-Roma slogans.
Small but at times violent demonstrations by nationalist youth then spread to 14 towns over the weekend.
On Tuesday night, the protests continued, and more than 160 people, mainly youths, were arrested, mostly for possession of weapons.
The BBC's Central Europe correspondent Nick Thorpe says predominantly Roma neighbourhoods are preparing to defend themselves from attack, as rumours spread on the internet.
Bulgarian leaders, including the prime minister and the president, have visited the village at the centre of the trouble, and insist that the violence is criminal, not ethnic.
A meeting of the National Security Council has been called for Saturday, to discuss the police response to the violence, ahead of elections later this month.
The unrest highlights tensions in Bulgaria, the poorest country in the European Union, as it struggles to emerge from deep economic recession.
The violence is thought to be the worst since 1997, when an economic crisis and hyperinflation brought Bulgarians onto the streets.
The Roma, or Gypsies, make up around 5% of Bulgaria's population of 7.4m.
Roma communities across Central Europe are poorly integrated and often have tense relations with their neighbours.