Some of the group were wearing ski masks and black military uniforms. They boarded buses which reportedly then took them to a location on Kiev's outskirts.
These were members of the Right Sector: an umbrella organization of far-right groups that has attracted a heavy share of international media attention, and has recently come into conflict with Ukraine's newly formed government.
The Right Sector was a small but influential group that formed part of the "self-defence units" in the recent anti-government protests on Kiev's Independence Square and elsewhere in the country.
The extent of their impact on the events that ultimately forced former President Viktor Yanukovych to flee Ukraine - and the number of people who ultimately make up their ranks - are hotly debated.
Nevertheless, it is generally accepted that at certain moments, they exerted an influence disproportionate to their seemingly small numbers.
But now the revolution is over, and the Right Sector - like many of the other self-defence groups - is still there on the square, sometimes equipped with firearms and often very aggressive.
Their presence has complicated the work of Ukraine's new leaders, who have struggled to demonstrate they are fully in control, after Russia's disputed annexation of Crimea and violent pro-Russian protests in eastern parts of the country.
What is more, Right Sector has bolstered the Kremlin's seemingly exaggerated claims that "fascists" have taken over Ukraine's government and are roaming the capital's streets, threatening minorities and Russian-speakers.
But now officials in Kiev may at last be tackling the thorny issue of Ukraine's radical far right groups.
The government and Right Sector have clashed a number of times in recent days. Acting Interior Minister Arsen Avakov has said all unofficial armed groups are operating illegally and must turn in their weapons.
Last week, a Right Sector leader from western Ukraine, Olexander Muzychko - who at one point was caught on video threatening a local council meeting with a gun and striking an official - was killed in a shoot-out with police.
Right Sector activists rejected officials' explanations that Mr Muzychko had fired on police first and then possibly shot himself. On Thursday, hundreds of them marched on parliament, demanding Mr Avakov's resignation and smashing windows.
Interim President Olexander Turchynov condemned the group's aggressive actions and said they were trying to "destabilise" Ukraine.
Now, with the Right Sector's early-morning retreat, the situation may be reaching its conclusion.
Late on Monday evening, an argument in Kiev's centre between a member of the group and another self-defence unit reportedly led to shots being fired. Three people, including a deputy mayor of Kiev, were injured.
The Right Sector activist found refuge in the Dnipro Hotel, the group's main headquarters. Riot police quickly surrounded the building and demanded all members of the group disarm and evacuate the building.
After a standoff lasting a few hours, they finally agreed and left the hotel.
The reaction to these events has been swift. Parliament voted unanimously for the "immediate disarming of illegally armed groups in Ukraine", which would also include pro-Russian groups in the country's east.
Criticism was also high among commentators and bloggers, who saw Right Sector providing fodder for Ukraine's critics.
"I'm calling on the leaders of the Right Sector. Guys, sort out the mess in your ranks," tweeted another self-defence leader, Volodymyr Parasyuk. "With these actions, you are discrediting [the revolution] and setting people against you."
The question that no one can answer at the moment is how much support, direct or tacit, Right Sector enjoys among the population at large.
At times during the anti-government movement they seemed to inspire the admiration of large numbers of people, who approved of their direct, violent methods to counter the brutality of Mr Yanukovych's government.
Ultimately, the issue of Right Sector's popularity and future viability may be determined by Ukraine's presidential elections on 25 May.
The group's leader, Dmytro Yarosh, is running in the contest. At the moment, though, he is polling just 1.6%.
But given that the group did not even exist a few months ago, some could view this as just the beginning.
Early on Tuesday, a group of young men - and a few young women - left the Dnipro Hotel in the centre of Kiev and marched through a cordon of heavily armed riot police.