Vladimir Putin has vowed to retaliate following a “terrorist” attack on the bridge linking Crimea to Russia.
Moscow has blamed Ukraine for the incident – which left two people dead – but Kyiv has not officially said it was responsible.
The Kerch bridge was opened in 2018 and enables road and rail travel between Russia and Crimea – Ukrainian territory annexed by Russia in 2014.
Russia’s transport ministry said the bridge’s supports were not damaged.
The ministry said investigations were continuing, but unconfirmed reports said explosions were heard early on Monday.
Russian authorities have accused Ukraine of attacking the Kerch bridge with two “unmanned surface vessels” (USVs) – drones that travel over water rather than through the air.
As yet, the BBC not seen any visual evidence to confirm this.
But a source in Ukraine’s security service told BBC Russian it was behind the attack and that water-based drones were used.
In televised comments on Monday evening, the Russian president accused Ukraine of launching the “senseless” and “cruel” attack.
The attack on the bridge has damaged the road it carries but the railway line running parallel to it have not been damaged.
The bridge is an important resupply route for Russian forces occupying parts of southern Ukraine.
Appearing on television with Mr Putin, Deputy Prime Minister Marat Khusnullin said the bridge would be completely repaired by 1 November, while road traffic would resume in one direction from 15 September.
Monday’s incident created long traffic jams on the remaining road route out of Crimea and severe train delays on the railway were reported. The ferry crossing that runs parallel to the bridge was also affected.
Russian officials urged holidaymakers stranded in Crimea to drive home through areas of southern Ukraine occupied by Russia since its army invaded last year. The officials said they would reduce curfew hours to let tourists through and that the army would keep the route “safe”.
Commercial flights between Russia and Crimea – a popular holiday destination for Russians since 2014 – have been suspended since Moscow’s invasion.
Vyacheslav Gladkov, governor of the western Russian region of Belgorod which is close to Russia’s border with Ukraine, said in a Telegram statement that a Russian couple had died in Monday’s incident. He added that their 14-year-old daughter had been injured.
Unverified photos posted by the spokesperson for Ukraine’s military administration in the Odesa region showed debris on the road across the bridge, as well as damaged railings.
Defence analyst Stuart Crawford told the BBC he believed that drones had been used to attack the bridge.
He also said details around what happened would likely remain unclear as neither side would want to release much information.
Russian foreign ministry spokeswoman Maria Zakharova accused Ukraine of attacking the Kerch bridge with the “direct participation” of the UK and the US, but provided no evidence to back up the assertions.
Kremlin spokesman Dmitry Peskov said there was no connection between the incident and Russia’s decision to suspend its participation in a deal allowing Ukraine to ship out grain through the Black Sea.
The alleged attack is the second major incident on the Kerch bridge in the past year.
In October 2022, the bridge was partially closed following a huge explosion. It was fully reopened in February.
Even now, the exact cause of the explosion last October remains unclear. Footage from the time showed a huge fireball erupting as a number of cars and lorries made their way across the bridge.
The latest incident comes amid a much-anticipated counter-offensive by Ukrainian forces which aims to retake territory in southern and eastern Ukraine.
Ukraine’s forces have retaken 18 sq km (7 sq miles) over the past week in their fightback, Ukraine’s deputy defence minister Hanna Maliar said on messaging app Telegram.
The recent gains take the total area of reclaimed land to 210 sq km (81 sq miles) since the counter-offensive began.
BBC
