Russia attacked the southern Ukrainian port of Pivdennyi on Saturday, Ukrainian officials said, as it ramped up strikes on the Odesa region along the Black Sea, including energy facilities and a critical route to the Moldova border.

Russia has unleashed an almost continuous drone and missile campaign against a region where ports critical to Ukraine’s foreign trade and fuel supplies operate, after Moscow threatened to cut “Ukraine off from the sea”.

Airstrikes have escalated even as the U.S. pursues an uphill diplomatic drive to broker an end to the war. U.S. negotiators were set to meet Russian officials in Florida on Saturday for the latest attempt to coax a deal out of Russia and Ukraine.

Saturday’s attack on Pivdennyi port hit reservoirs, Ukrainian Deputy Prime Minister Oleksiy Kuleba said on the Telegram messaging app, a day after a missile strike on the port that killed eight people and injured at least 30.

On Thursday and Friday, Russian forces targeted a bridge on the Dniester river estuary near the village of Mayaky, northeast of Pivdennyi, Ukrainian officials said.

The bridge connects parts of the region fragmented by the undulating sea coast and river estuaries, and is the only main route towards Moldova’s border crossings to the west.

“Without significant success on the (battle) front, the enemy is trying to terrorise civilians to create internal destabilisation. These plans are clear, and we are effectively countering them together with the people of Odesa,” deputy presidential administration head Viktor Mykyta said on Telegram.

Russian officials have not commented on the attacks.

Ukrainian authorities temporarily re-routed passengers to other crossings, including by water, into Moldova. Mykyta said Ukraine would create as many alternative crossings as necessary, “no matter how hard the enemy tries to destroy the connection”.

Last week, one of the war’s biggest Russian air attacks on the strategic Black Sea region damaged energy facilities and prompted a blackout in Odesa, plunging hundreds of thousands of civilians into darkness for days.

Airstrikes on ports damaged three Turkish-flagged vessels in December.

Russian President Vladimir Putin has vowed to cut Ukraine’s access to the Black Sea in retaliation for Kyiv’s maritime drone attacks on Moscow’s sanctions-busting “shadow-fleet” tankers.

Ukraine says those vessels are used to transport oil, Russia’s main revenue source for funding its almost four-year-old full-scale invasion of its neighbour.