A well-known journalist and opposition activist in Ukraine has been beaten up by unknown attackers.

Tetyana Chornovol told police her car was stopped by a gang of men near Kyiv just after midnight on Wednesday morning. She was dragged from the vehicle, assaulted and left in a ditch.

The reporter had just published an article on the personal wealth of Ukraine’s Interior Minister Vitaly Zakharchenko, highlighting a “country manor” near Kyiv. She has also been investigating the assets of several other political leaders.

There is no evidence connecting any of them to the attack.

On Wednesday in the capital several hundred supporters of the journalist protested outside the Interior Ministry, demanding an inquiry.

“According to the doctors she has concussion and head injuries,” said Oleksii Grytsenko, a friend of Tetyana Chornovol. “She tried to run away, but they caught her, someone broke the window in her car and then beat her. What happened next, Tetyana could not remember. She regained consciousness in hospital.”

In a video posted on YouTube, the journalist said she did not recall her attackers saying anything as they beat her.

The opposition website Pravda published a video showing a car chase said to have preceded the attack, purportedly filmed from Chornovol’s dashboard camera. The date reads 2010, but friends of the journalist say it had only recently been installed and not set properly.

The attack follows at least one other reported assault on a government opponent in recent days.

Another demonstrator at the protest in Kyiv said: “I think this shows the weakness of this government. When people cannot use arguments or evidence, they start beating people up. What’s more, they are beating a woman, a mother. That is unacceptable.”

Government opponents quoted in Ukrainian media say they have identified the car used in the assault as belonging to the ruling Party of Regions.

President Yanukovych has condemned the attack and ordered law enforcers to find those responsible.