Moscow: A car bomb-caused fire has started on a vital road and rail bridge connecting Crimea to Russia, which annexed the region from Ukraine in 2014, according to Moscow authorities on Saturday.

The national anti-terrorism committee was quoted by Russian news agencies as saying that a car bomb exploded today at 6:07 a.m. (0307 GMT) on the road traffic side of the Crimean bridge, causing seven oil tankers being transported to Crimea by rail to catch fire.

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The bridge, which Russian President Vladimir Putin ordered built and opened in 2018, was a crucial transportation route for ferrying troops and delivering military supplies to Russian soldiers fighting in Ukraine, particularly in the south.

Despite the fighting in Ukraine, Russia insisted the bridge was secure and threatened Kyiv with retaliation if it came under attack.

Local Russian official Oleg Kryuchkov was quoted by RIA-Novosti and the Tass news agency as saying that an object believed to be a fuel storage tank caught fire and that traffic has been halted on the bridge.

Social media posts included pictures that allegedly showed the span in flames and damaged. The reports' and images' veracity couldn't be immediately confirmed.

The crossing is a pair of rail and road bridges that Russia constructed after it illegally took the Crimean Peninsula from Ukraine in 2014 and annexed it.

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The explosions that shook the city of Kharkiv in eastern Ukraine early on Saturday morning sent towering plumes of smoke into the sky and set off a string of subsequent explosions. The fire broke out hours later.

Ihor Terekhov, the mayor of Kharkiv, claimed on Telegram that missile strikes in the city's core were the cause of the early-morning explosions. He claimed that one of the city's medical facilities and a non-residential building both caught fire as a result of the explosions. There were no reports of casualties right away.

The explosions occurred hours after Russia focused its troubled invasion of Ukraine on regions it had forcibly annexed, and as the death toll from earlier missile strikes on apartment buildings in the southern city of Zaporizhzhia reached 14.

The Norwegian Nobel Committee presented the Nobel Peace Prize on Friday to human rights groups in Russia, Ukraine, and a jailed activist from Belarus, a close ally of Moscow.

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The award was given to "three outstanding champions of human rights, democracy, and peaceful coexistence," according to the committee's chair, Berit Reiss-Andersen. However, this was widely interpreted as a criticism of Russian President Vladimir Putin and his handling of the worst armed conflict in Europe since World War II.

This week, Putin made illegal claims to four Ukrainian regions, including the Zaporizhzhia region, which houses the biggest nuclear power plant in Europe, whose reactors were shut down last month.