In the dead of night, Ukrainian border guards in the eastern locality of Marinovka open fire on a group of armed men trying to sneak across from Russia.
It is around 3am, and a convoy of around 40 trucks, minibuses and cars are trying to bring teams of pro-Russian militants into eastern Ukraine.
The Ukrainian forces ended up killing one assailant and managed to stop several vehicles, seizing men and weapons, border guard spokesman Oleg Slobodian later told local station Kanal 5.
But they were not able to stop the whole of the convoy from breaking through the line.
Such clashes are becoming increasingly common, according to the government in Kiev, which says the border has become a frontline in the battle with separatists seeking to wrest control of the country's east.
"Attempts to cross the border between Russia and Ukraine have become more frequent, especially in the last two weeks," Sergei Astakhov, number two in the Ukrainian border guards, told AFP.
"Today, we consider the border a frontline where we have near-daily armed clashes."
- Easy to cross -
The border post at Marinovka lies just 90 kilometres (55 miles) from the regional city of Donetsk, the stronghold of pro-Russian rebels, where the flag of the "People's Republic of Donetsk" flies proudly over barricades.
"If we really wanted, we could cross the border on foot, especially at night," said a Marinovka resident, 24-year-old Olexy.
"Many guys in the region cross for petrol or car parts, which are cheaper in Russia. We know perfectly well where we need to cross."
While the border guards were clashing with trespassers at Marinovka, another group was trying to cross the border in the neighbouring region of Lugansk, near the village of Astakhov, Ukraine authorities said.
"The routing of Russian terrorists into Ukraine is organised and financed through the Kremlin at Russian secret services," said Ukraine's foreign minister, demanding that the "Kremlin stop sending terrorists and arms into Ukraine."
At the Marinovka checkpoint, no more than a dozen soldiers can be seen. The occasional vehicle passes in one direction or the other, weaving through large concrete blocks and sandbags.
The protection measures seem modest given that they could be attacked by the rebels at any point, as several checkpoint have been in recent weeks.
In the Donetsk and Lugansk regions, groups of 30 or 40 militants have assaulted such positions, although they have so far been repulsed by security forces.
That contrasts with the police and secret service forces in several towns in eastern Ukraine, who have frequently abandoned their posts and allowed the rebels to seize control of administrative buildings.
The self-proclaimed "Republic of Donetsk" has requested annexation by Russia -- a demand that has yet to receive a response from Moscow. In the meantime, opening the borders has become a key demand of the separatists.
Near the border at Marinovka, a woman who doesn't wish to be named, sums up a common attitude: "Here, we've never really had the feeling that there is a border with Russia."