Why the Crimean Bridge is key to Russia's war in Ukraine

LONDON -- A series of explosions damaged a section of the single bridge that connects Russia to Crimea on Monday, marking the latest attack on Moscow's crucial link to the annexed peninsula.

The blasts occurred before dawn, killing a married couple and wounding their daughter, according to Russian state media. The Crimean Bridge -- the longest in Europe -- remains open to trains but is now closed to road traffic as Russian authorities assess the damage before determining how long it will take to repair. Footage from the scene on Monday morning showed a damaged section tilted and hanging down.

Russian officials said the strike was carried out by Ukrainian sea drones and described the incident as a terror attack. Ukrainian officials have not yet commented publicly on the matter.

It's the second major strike on the Crimean Bridge since last October, when a truck loaded with explosives blew up both the road and rail sections. Repairs took months, with the roadway reopening in February and the rail side in May.

Russian troops invaded and subsequently annexed the Crimean Peninsula from neighboring Ukraine in 2014, a move that most of the world denounced as illegal and prompted both the United States and the European Union to impose sanctions on Moscow. But Russian President Vladimir Putin defied the criticism and ordered the construction of a $3.6 billion bridge spanning nearly 12 miles across the Kerch Strait, which separates mainland Russia from Crimea.

After two years of construction, Putin announced the opening of the road section of the Crimean Bridge in 2018. The rail section was finished the following year.

The bridge established Russia's first land link to Crimea -- connecting the southern Russian region of Krasnodar to the peninsula's port of Kerch -- and, thus, is laden with symbolism. Moscow has portrayed the bridge as a physical affirmation of Crimea's incorporation into Russia. Crimea's only other land crossing leads into the rest of Ukraine and, until the bridge's completion, vehicles traveling from Russia have had to rely on ferries across the Kerch Strait that are frequently interrupted by bad weather.

The Crimean Bridge has become a key supply route for the Russian military since its forces invaded Ukraine again in 2022, with the conflict spiraling into an all-out war. The bridge remains essential for Russia's military operations in southern Ukraine as Ukrainian troops wage a major counteroffensive to take back Russian-seized territory.

Recently, Ukrainian forces have also targeted other bridges connecting Crimea to the southern areas, which analysts said is an effort to break down Russia's ability to supply its lines in the Zaporozhzhia and Kherson regions.

ABC News' Joe Simonetti contributed to this report.