Kremlin says guard unit is there to prevent ‘infiltration’ of its territory and denies any movement across the border

Russia has denied that its troops entered Ukrainian territory, saying that a column of armoured vehicles spotted on the border was a unit of border guards patrolling the frontier.

A day after the Guardian and Daily Telegraph reported seeing 23 Russian armoured personnel carriers, supported by fuel trucks and other military logistics vehicles, crossing into Ukrainian territory, the FSB said there was a detachment in the area of border guards set up to assure safety and “prevent the infiltration of armed people on the territory of the Russian federation”.

But the security service stressed that the unit operated exclusively on Russian territory. “In this regard, information on a group of Russian soldiers crossing the Russian-Ukrainian border is not true,” RIA Novosti quoted an official as saying.

The Guardian and Telegraph reported reported witnessing the convoy crossing into Ukrainian territory on Thursday night through what appeared to be a gap in a wire fence that demarcates the border, close to the village of Severny, on the Ukrainian side. The ultimate destination of the convoy was impossible to verify.

Shaun Walker (@shaunwalker7) So @RolandOliphant and I just saw a column of APCs and vehicles with official Russian military plates cross border into Ukraine.

The reports drew swift international reaction. The foreign secretary, Philip Hammond, on Friday said that any incursion could have very serious consequences.

“I’m very alarmed by reports that Russian military vehicles may have crossed the border this morning. If there are any Russian military personnel or vehicles in eastern Ukraine, they need to be withdrawn immediately.”

On Thursday, the Guardian again travelled to the site to look at the area in daylight. The fence, which demarcates the border and runs along the outside suburbs of the Russian border town of Donetsk, is permeated by informal crossings and dirt tracks. Around the area where the Guardian saw the crossing the day before, a truck was parked with Russian military plates, on the Russian side. It was not possible to linger as the area is a restricted border zone, but military vehicles with no plates were seen coming from the direction of Ukraine.

Also during the day, there was further large-scale movement of military hardware along the road between the border Kremensk-Shakhtinsky, where a caravan of more than 200 white aid trucks is camped, awaiting onward shipment to eastern Ukraine where it is to deliver a consignment of humanitarian aid. The Guardian saw at least 50 APCs and dozens of trucks and troop carrying vehicles, many emblazoned with “peacekeeping forces” and some flying the Russian flag, on the road.

The aid convoy set off from a Russian military base on Tuesday. Russia insists the convoy includes badly needed aid for residents trapped in Luhansk for almost two weeks without water and electricity.

Tom Barton (@TomBartonJourno) No Russian convoy trucks to be seen at Donetsk (small Russian town, not Ukrainian city) border crossing. All still parked up.

Some have turned out to be nearly empty. According to the FT’s Courtney Weaver, Russia’s emergency services say they want reserve trucks in case some break down:

Courtney Weaver (@courtneymoscow) Got to check out more convoy trucks this morning. A lot of them mostly empty like this one pic.twitter.com/9qM7bYliv9

She concludes: “Seems more like the trucks were hastily packed/not enough time for all to be filled completely”

According to the BBC’s Daniel Sandford, meanwhile, the Red Cross says the large Russian escort travelling with the convoy won’t be allowed into Ukraine: