Russia has finished building a high-tech security fence along annexed Crimea’s border with mainland Ukraine.
The fence, more than 60km (37 miles) long, is topped with barbed wire and has hundreds of sensors.
Russian forces annexed Ukraine’s Crimea peninsula in March 2014 – a move condemned internationally. Crimea has a Russian-speaking majority.
Russia’s FSB security agency says the fence is necessary to prevent “infiltration attempts by saboteurs”.
An FSB statement, quoted by Russia’s RIA Novosti news agency, said the fence would also thwart smugglers trading in illegal weapons, drugs, alcohol and other contraband.
The fence spans the neck of land connecting Crimea with Ukraine’s Kherson region.
Most of its sensors pick up vibrations from any potential intruders, the FSB said, but some are also radio-location devices. Russia has similar equipment along its northern and eastern borders.
On Wednesday Ukrainian President Petro Poroshenko lifted martial law in the country’s border regions, which was imposed last month after Russia seized three Ukrainian naval vessels in the Sea of Azov.
Ukraine has also erected border fences since Russia’s 2014 annexation of Crimea and the pro-Russian insurgency in eastern Ukraine. New fences went up in the Chernihiv and Kharkiv regions, north of Kiev – regions bordering on Russia. Ukraine also has a new fence in Kherson region, near Crimea.