Ukraine's army chief said Wednesday the situation on the battlefield was "difficult" and that Russian forces could be poised to strike deep into Ukrainian lines in the eastern Donetsk region.

Ukrainian long-range drones smashed into two oil facilities deep inside Russia on Tuesday, officials said, while an armed incursion claimed by Ukraine-based Russian opponents of the Kremlin unnerved a border region just days before Russia's presidential election.

One person was killed and 22 were injured in a suspected gas explosion in northern China's Hebei province Wednesday, state media reported.

The explosion was suspected to have been caused by a gas leak at a fried chicken shop in the city of Sanhe just before 8 am (0000 GMT), state broadcaster CCTV reported.

Joe Biden and rival Donald Trump have won enough delegates to clinch their party nominations in the 2024 presidential race, networks projected, all but assuring a rematch and setting up one of the longest general election campaigns in U.S. history.

The results in Georgia, Mississippi, and Washington state were essentially a foregone conclusion as President Biden and opponent Trump had already disposed of all primary challengers, and winning the Tuesday votes pushed them both over the threshold of delegates needed to become their parties' nominees in the November election.

President Vladimir Putin said that Russia is ready to use nuclear weapons if there is a threat to its statehood, sovereignty or independence, voicing hope that the U.S. would refrain from actions that could trigger a nuclear conflict.

Putin's statement was another blunt warning to the West ahead of a presidential vote this week in which he's all but certain to win another six-year term.

The French navy frigate, bristling with weaponry and powering through frigid Norwegian seas not so far from Russia, awoke at 7:30 a.m. sharp to what, in the circumstances, was a surreal sound.

The 1967 " Summer of Love " hippie anthem "San Francisco (Be Sure to Wear Flowers in Your Hair)" was playing over the warship's public address system. Singer Scott McKenzie's voice reverberated through the passageways starting to bustle with sailors clutching coffee mugs: "All across the nation, such a strange vibration, people in motion."

Ukraine launched a wave of long-range drones against targets deep inside Russia on Tuesday, Russian officials said, hitting at least two oil facilities in the attack on eight regions of Russia in the latest display of Kyiv's expanding drone capacity.

Also Tuesday, soldiers who Kyiv officials say are Russian volunteers fighting for Ukraine reported to have crossed the border into Russia, as they have several times during the war. Russia said it had beaten back attempted incursions, but it wasn't possible to verify either side's claims and the reports of border fighting were murky.

China, Iran and Russia have begun a joint naval drill in the Gulf of Oman, a crucial waterway near the mouth of the Persian Gulf, officials said Tuesday.

Footage aired by Chinese state television and a video released by the Russian navy showed the ongoing drill, known as "Marine Security Belt 2024."

Moscow on Tuesday said its army had beaten back Ukrainian forces trying to claim territory in two Russian border regions, deploying warplanes, missiles and artillery to fend off the assaults.

The defence ministry said in a statement that Russian forces "thwarted an attempt by the Kyiv regime to make a breakthrough into the border territory of the Russian Federation in the Belgorod and Kursk regions".

Thousands of Russians braved the cold for hours earlier this month to honor the opposition politician Alexei Navalny after his funeral. They chanted anti-war slogans and covered his gravesite with so many flowers that it disappeared from view.

It was one of the largest displays of defiance against President Vladimir Putin since he invaded Ukraine, and happened just weeks before an election he is all but assured to win. But Russians watching television saw none of it.