Russia said its lead warship in the Black Sea sank after an explosion and fire that Ukraine claimed was caused by a missile strike, dealing a blow to Moscow as it readied for new attacks that were likely to determine the conflict's outcome.
The Moskva, Russia's flagship in its Black Sea fleet, sank as it was being towed to port in stormy weather, Russian news agencies quoted the defence ministry as saying.
Russia said earlier that over 500 crew aboard the Soviet-era missile cruiser were evacuated after ammunition on board exploded.
Ukraine said it hit the warship with its domestic Neptune anti-ship missile.
Neptune missile modelled on Soviet Kh-35 anti-ship missile
Neptune is a Ukrainian anti-ship cruise missile based on the Soviet Kh-35 anti-ship missile. The first test of the missile was conducted in 2016 and it underwent couple of tests in subsequent years.
The sinking of the Moskva came as a shock as it is the largest warship Russia has lost in combat since World War-II.
Reports claim Russian frigate Admiral Essen was earlier damaged due to the Neptune missile strike, however, it could not be confirmed.
'Big blow' to Russia
The domestically built Neptune can be launched from a truck and has a range of 25 kilometres from the coast and has maximum range of about 300 kilometres.
The Pentagon had said the sinking of the warship Moskva after it was engulfed in an inferno was a "big blow" to Russia's naval strength in the Black Sea.
Pentagon officials were unable to confirm or deny Ukraine's claim of Neptune missile strike on the Moskva.
"It's certainly plausible and possible that they did in fact hit this with a Neptune missile or maybe more," Pentagon spokesman John Kirby said.
Harpoon anti-ship missiles
As the war in Ukraine enters in a new phase with Russian troops concentrating their forces in eastern Donbas area, the UK said it will supply heavier weapons and armoured combat vehicles to support Ukraine.
Among them is the Harpoon anti-ship missiles to break Russia's dominance in the Black Sea region. Russian Navy has been launching missiles from its warships on Ukraine.
Ukraine's strategic Black Sea port of Odessa has repeated been hit by missiles in the past few weeks.
Russian artillery pounds Ukraine
Joe Biden has promised to help Ukraine get air defense systems with a longer range than the shoulder-borne Stinger missiles already on the ground, but finding the powerful anti-missile batteries Ukraine's military so urgently needs is proving easier said than done.
The US president, who wants to support Ukraine militarily without entering into direct conflict with Russia, is seeking to provide better defenses against the Russian artillery that is pounding its cities.
Patriot system vs Russian missile arsenal
The ideal armament to do that would be mobile anti-aircraft batteries of the Patriot type, whose effectiveness has been amply demonstrated in recent years in Iraq and the Persian Gulf.
Still unclear is whether the Patriot system could provide an effective defense against the latest missiles in the Russian arsenal.
S-300 anti-aircraft system for Ukraine
Ukraine's army, moreover, is not at present trained to handle the sophisticated US Patriot system.
On the other hand, they know how to handle the S-300 anti-aircraft system, a first-generation Russian competitor to the US Patriot, whose range is more limited but which would be sufficient to protect Kharkiv or Kyiv, two cities close to the Russian border, where most of the missiles that pound them are fired from.
Ukraine had around 100 S-300 batteries before President Vladimir Putin launched his invasion last month, and the Russian army claims to have destroyed about 40 at the very outset of the war on February 24, Eastwood, a former US soldier, recently wrote.
The Gulf countries have numerous anti-aircraft batteries to protect themselves from Iranian missiles, but they do not seem in a hurry to come to the aid of Ukraine.
Saudi Arabia and the United Arab Emirates, which are among the world's biggest crude exporters and both have strong ties to both the West and to Moscow, have so far avoided taking any stance against Russia.