KYIV -- Friends and relatives of Dmytro Bulatov are increasingly worried.
The Ukrainian antigovernment activist disappeared without a trace on January 23 -- the day after another opposition sympathizer, scientist Yuriy Verbytsky, was found dead with traces of torture in a forest
Bulatov is the spokesman for Automaidan, a group of motorists founded in late November to support Ukraine's European integration and counter police assaults against pro-EU demonstrators in their two-month standoff with authorities.
The popularity of its rallies-on-wheels and the rapid-response network it has set up to rescue demonstrators from police have propelled the group to the forefront of the protests.
Its activists routinely meet with opposition leaders, address protesters on Kyiv's Independence Square, and have held talks with U.S. and European envoys.
And the authorities appear to have woken up to the threat posed by Automaidan and its 5,000 activists.
No Large Convoys
A controversial new law that effectively prohibits large rallies now bars motorists from traveling in convoys of more than five vehicles.
And in the night that followed Bulatov's disappearance, riot police launched four separate raids on Automaidan, beating and detaining more than 20 of its activists as they patrolled the streets of Kyiv in their vehicles.
A video recorded by one of the activists' dashboard cameras shows police officers smashing the car's windows with their truncheons. The passengers are then heard screaming and calling on the officers to end the violence.
Olesya Mamchich, the wife of one of the detained activists, told RFE/RL that "they were dragged out of their cars. There were two women who were eventually released. But the men were beaten up. He said the officers kicked their heads and arms."
Mamchich says her husband and his friends were ambushed by police after receiving a fake call for help.
Ukraine's Interior Ministry, in turn, accuses the activists of chasing police officers before smashing their vehicles with baseball bats.
Police spokesman Sergiy Burlakov told RFE/RL: "Some of them, 18 people, were detained in connection with the incident on Krypostny street, where they were blocking Berkut vans and assaulted police officers."
Although footage of the incident contradicts these claims, the activists were charged with hooliganism and resisting arrest. They face up to six years in prison if convicted.
Automaidan's founder is Oleksiy Hrytsenko, a local IT company manager who is also the son of opposition politician Anatoliy Hrytsenko.
He told RFE/RL in written comments that authorities are cracking down on Automaidan because it "succeeded in making them nervous."
Hrytsenko has stopped giving telephone interviews, saying his calls are monitored.
He says his group is popular because it represents the backbone of Ukrainian society -- middle-class professionals with a car and a desire to live in what he calls "a normal country."
About one-third of its activists are women, including journalist Tetyana Chornovol, who was pulled out of her car by unidentified men last month and viciously beaten up.
Automaidan members have reported numerous cases of intimidation, threats, and assaults.
Hrytsenko says he is being stalked and has received threatening text messages on his phone. On several occasions, his father received anonymous SMS messages informing him that his son was dead.
Another Automaidan leader, Sergiy Khadzhinov, was abducted while blocking a road to prevent riot police from reaching the Euromaidan protests on Kyiv's Independence Square.
He was seized by a group of men who pulled a bag over his head and pushed him into a car.
His abductors turned out to be officers from Ukraine's crime-busting police unit who took him to a police station and questioned him for several hours before releasing him unharmed.
His computer, mobile phone, documents, the key to his flat, and 2,000 hryvnia ($230) were however confiscated and never returned.
Bulatov, too, had received threats.
A father of three, he had been sent toys smeared with zelyonka, the green antiseptic solution widely used to treat child injuries in former Soviet countries.
But like his fellow Automaidan activists, he had pledged not to cave in to pressure.
He told "Ukrainska Pravda" in an article published on the day he went missing that "Even if something happens to me, resentment will only grow. And if it helps get us closer to victory, then let it be."
Iryna Stelmakh reported from Kyiv. Claire Bigg reported and wrote from Prague