The Kerch bridge connecting the mainland to Crimea is under threat from dissatisfied Wagner fighters who have turned against Vladimir Putin, according to Russia.
Due to rigorous security checks, there were significant delays of up to seven hours for tourists seeking to pass the bridge to get to the Black Sea peninsula.
According to the citizen information agency InformNapalm, they went to great lengths, including sending kids to obtain x-rays and checking every component of the cars, even the glove compartments.
The 10-mile bridge, which was built at a cost of around £3 billion, links annexed Crimea to the Taman Peninsula of Krasnodar Krai on mainland Russia.
Delays also hit the nearby truck ferry service between the mainland and Crimea.
Concerns have been raised that angry Wagner fighters could be planning a violent bomb attack after Putin axed their army, according to a report.
The private army was central to one of the most dramatic days in recent Russian history last month, when Wagner leader Yevgeny Prigozhin ordered it to march on Moscow as he raged about perceived mismanagement of the war in Ukraine.
Russians and governments around the world were preparing for the real possibility of a coup on June 23, before Prigozhin abruptly called off the march.
His soldiers left the southern military HQ at Rostov-on-Don, which they reportedly took over without much resistance, and he is believed to have left for Belarus under the terms of a deal brokered by Belarusian president Alexander Lukashenko.
There are now worries Wagner mercenaries may attack the bridge, amid apparent anger that Putin may be reneging on the deal.
According to the Mirror, Telegram channel InformNapalm shared evidence for these fears.
The channel said: ‘Obviously, saboteurs are expected in Crimea.
‘It is possible that some attentive people passed information to the FSB that the Wagnerites are preparing to bring explosives and ammunition to Crimea, because the agreements on the part of the Kremlin have not been fully implemented.’
It is expected that some Wagner fighters will join Prigozhin in exile in Belarus while others will join the regular Russian army.
The delays over security checks for people crossing the Kerch bridge weren’t generally received well.
Nikolai Lukashenko, appointed by Putin to be in charge of transport in Crimea, said: ‘Staff numbers on the inspection lines have been increased and control over their work has been strengthened.
‘We apologise to citizens for the inconvenience.’
Many Russians are spending the summer in Crimea despite it being a possible target, because Western restrictions mean they can’t head to popular holiday destinations.
A bomb blast on a truck which was driving across the bridge in October last year also caused major damage to the Kerch Strait, and has been blamed on Ukraine.