The prisoner swap between Ukraine and Russia Saturday has prompted hopes that Moscow and Kyiv are ready for serious talks to end a more than five-year war in the Donbas region of eastern Ukraine - a Moscow-fomented conflict that's claimed more than 13,000 lives.

As the exchange unfolded, which included the release by Russia of 24 sailors captured in a naval clash last November, U.S. President Donald Trump tweeted, "Russia and Ukraine just swapped large numbers of prisoners. Very good news, perhaps a first giant step to peace. Congratulations to both countries!"

That view was shared by the man who engineered the swap, Ukraine's President Volodymyr Zelenskiy, who hailed the exchange as "the first step to end the war." And various other Western leaders, including Germany's Angela Merkel and France's Emmanuel Macron, joined the chorus lauding the exchange of 70 prisoners in all as a positive move.

For the families of those exchanged, there was relief.

Russia had threatened to incarcerate the sailors for up to six years, saying their patrol boats had trespassed into Russian territory by crossing its borders to enter the Sea of Azov, just off Crimea, the Ukrainian peninsula annexed by Russia in 2014.

Ukraine and other countries that don't recognize Russia's annexation of Crimea say the sailors were in international waters, and an international maritime court ordered Moscow to free the men, an instruction ignored until Saturday.

Others among the 35 Ukrainian detainees had been held for years, including Oleg Sentsov, a filmmaker who was serving a 20-year sentence in an Arctic penal colony on charges of "terrorism."

On their arrival at Kyiv's Boryspil airport, where they were greeted by relatives and Zelenskiy, there was euphoria.

"Hell has ended. Everyone is alive, and that is the main thing," said Vyacheslav Zinchenko, one of the sailors.

Russian President Vladimir Putin did not greet in Moscow the 35 Russians released by Kyiv.

Since his surprise election earlier this year, Zelenskiy, a political novice and former television comic, has been urging Putin to join a new round of peace talks involving Trump and other Western leaders.

In a video statement released in July to coincide with a one-day EU-Ukraine summit in Kyiv, Zelenskiy appealed to Putin directly.

"We need to talk. We do. Let's do it," he said, looking directly into the camera.

Last month, it was announced the leaders of Russia, Ukraine, France and Germany would meet to discuss the Donbas conflict. But in an interview in July with VOA's Ukrainian Service, Kurt Volker, U.S. special representative for Ukraine negotiations, cautioned against optimism.

"Unfortunately, we've really not heard much news from Russia. They are still saying that everything is Ukraine's responsibility, that Ukraine needs to negotiate with the two so-called separatist 'People's Republic' that they created in Ukraine," he said, referring to the Kremlin-backed, self-proclaimed republics of Donetsk and Luhansk.

'Sinister' exchange

While some are seizing on the prisoner exchange as the possible start of something new, for others it has triggered worries that Putin is using Ukraine to toy with the West. Skeptics argue that Putin isn't serious about ending a conflict of his own making and has every reason to nurture it as a way to disrupt Ukraine and continue to punish the country for its popular Maidan uprising in 2014, which forced Viktor Yanukovych, a Putin ally, out of power.

They highlight the imbalance in the prisoner swap - seeing Putin's approach to it as displaying a sinister cynicism. While the released Ukrainians had been held on trumped-up charges, their Russian and pro-Moscow separatist counterparts weren't innocent. They included Volodymyr Tsemakh, who commanded a Russian separatist air defense unit close to where Malaysian Airlines Flight MH17, enroute to Kuala Lumpur from Amsterdam, was shot down in 2014, killing all 298 people onboard.

The Dutch government has been left fuming, saying it "seriously regrets that under pressure from the Russian Federation, Tsemakh was included in this prisoner swap."

Ukrainian politicians had pleaded with Zelenskiy not to release Tsemakh, but his freedom apparently was the price the Ukrainian leader was forced to pay for the prisoner exchange.

Dutch Foreign Minister Stef Blok said the Netherlands was "deeply disappointed" by the release, but added Ukraine had delayed the prisoner exchange to let Dutch investigators question Tsemakh before he was freed.

According to Marcel Van Herpen, author of the book "Putin's Wars," and a director at the Cicero Foundation research group, Tsemakh's release could be a complicating factor for the MH17 trial, which starts in March 2020 in The Hague.

"Of course we are all happy they and the others are free," tweeted self-exiled Russian dissident Garry Kasparov. "But this is not justice. Putin takes innocent hostages to use as bargaining chips. He is rewarded and praised for exchanging them for Russian spies & criminals, encouraging further terrorist acts."

Kasparov and other skeptics worry that amid heightened talk of efforts to normalize relations with Putin, the West will fall into the pattern of giving ground to Putin.

"New talk of a 'peace process' is a joke when Putin could end the conflict instantly, just as he began it. 'Use force, then negotiate' works well for him," Kasparov tweeted.

Michael Carpenter, a senior fellow at the Atlantic Council, is cautious about interpreting "this as a step toward ending the war." He noted, "August was one of the bloodiest months in the Donbas in a long time. More importantly, no country is incentivizing Putin to "de-escalate." Other analysts fear the swap makes Russia appear reasonable when it was the aggressor state.

Willem Aldershoff, a former senior EU diplomat, worries that Western leaders keen for a reset in relations with Moscow will "be less confrontational with Putin" and "will use this 'new Russian flexibility' to pressure Zelenskiy to make compromises that aren't in Ukraine's best interests.