A rescue worker holds an injured boy after what activists said were airstrikes carried out by the Russian air force in Idlib city, Syria December 20, 2015. Ammar Abdullah/Reuters On Sunday, Russian airstrikes over a busy marketplace in the rebel-held city of Idlib, Syria, killed at least 70 civilians and wounded dozens more.

“We’ve never been bombed like this," Issa Khaled, a resident of the Aleppo suburb of Ghouta, told The Guardian the day after the attack.

"The skies above us looked like Hiroshima," he said, referring to the Japanese city targeted by an atomic bomb during World War II. "There were clouds like mushrooms everywhere we looked. The destruction was incredible."

In retaliation for Turkey's decision to down a Russian warplane late last month, Moscow has stepped up its bombing raids across the north, near the Turkish-Syrian border.

The raids, targeting rebel supply lines and civilian infrastructure, have created "an emerging humanitarian crisis" and exacerbated a refugee crisis that already has Europe near its breaking point.

“We’re seeing a huge increase in the number of civilian casualties. More and more people are being hurt because the intensity of bombing is greater,” Rae McGrath, country director for Turkey and North Syria for the American aid agency Mercy Corps, told The Washington Post's Liz Sly.

McGrath added: “It’s hard to imagine that the conditions in Syria could have become worse than they already were, but they have.”

People inspect a site hit by what activists said were airstrikes carried out by the Russian air force in Idlib city, Syria December 20, 2015. Ammar Abdullah/Reuters

US President Barack Obama has repeatedly expressed his belief that the Russians — who began their air campaign in Syria on September 30 on behalf of the Syrian government — will get bogged down and ultimately withdraw from the conflict. But as time goes by, the Russian air campaign is becoming only more intense.

"Expectations by each player that its foes will ultimately sink into the Syrian quagmire are perhaps sound in the grand-power game," Joseph Bahout wrote for the Carnegie Foundation's Syria in Crisis blog.

"Nevertheless, this will mean the slow death of Syria, with disastrous spillover effects for the wider region."

A man runs through dust in a site hit by what activists said were airstrikes carried out by the Russian air force in the rebel-controlled area of Maaret al-Numan town in Idlib province, Syria October 24, 2015. Khalil Ashawi/Reuters Russia's air campaign — which, with its reported strikes on marketplaces and ambulances, seems less concerned with collateral damage than the US-led coalition — has been compared to that of the Syrian government, which is known to target bakeries, schools, and hospitals using primitive barrel bombs.

Russian bombs, however, are not as imprecise as the steel barrels packed with explosives and shrapnel dropped by the regime's helicopters. And they appear to be more relentless.

“Where are these reasonable Russians that [US Secretary of State John] Kerry claims are starting to see the light?” a doctor in an Idlib hospital asked The Guardian on Monday.

“Bashar’s jets never bombed us like the Russians do," the doctor said, referring to the forces that support the regime of Syrian President Bashar Assad. "ISIS never hunted us down like this."

Moscow, for its part, denies that it is deliberately targeting anyone other than "terrorists."

“We are talking exclusively about terrorist groups and where they are located, and in no way is civilian infrastructure a target for Russia’s air force," ministry spokeswoman Maria Zakharova said at a recent briefing, according to The Wall Street Journal.

"Any objective observer cannot have a shadow of a doubt about the true intentions of Russia’s airstrikes."

Putin 'gains a lot'

At a marathon press conference last Thursday, Putin signaled Russia's intention to stay the course of the war in Syria.

"It's hard to imagine a better exercise" for Russian forces, Putin said. "So we can train there for a long time without any serious harm to our budget."

He may not have been bluffing: Mark Kramer, the program director for the Project on Cold War Studies at Harvard's Davis Center for Russian and Eurasian Studies, told Business Insider on Saturday that a long-term Russian campaign in Syria is sustainable — for now.

The S-400 SAM system is capable of contesting most of the airspace over Syria, southern Turkey, northern Jordan, a significant portion of Israel, as well as all of Lebanon and Cyprus. Institute for the Study of War

"This sort of operation would have been unsustainable for Russia a decade ago, but Russia's military buildup since 2009 has greatly improved the readiness and deployability of Russian forces," he said.

Hence, Kramer added, they can probably sustain the current level of operations for a while.

"Only if the hostilities escalate and Russian ground forces are deployed to Syria in sizable numbers will it begin to pose serious problems," he said.

Additionally, while the airstrikes are a "tremendous drain on Russian resources" and have not resulted in any game-changing regime victories on the ground, Putin ultimately "gains a lot, much more than in his previous projects," by maintaining the pace of his intervention, said Andrei Korobkov, a professor of post-Soviet relations at Middle Tennessee State University.

"With this incursion, Putin has returned Russia to a major power status, becoming a key player in the Middle East," Korobkov told Business Insider on Saturday.

"He brought S-400 ABM systems to Syria that effectively allow him to seal off the skies to everybody else, and now has a very effective way to advertise Russia's newest weapons on the world market — i.e., by testing them in action."

"Judging by the events following Kerry's visit [to Moscow], he is also getting concessions from the West," Korobkov added.

In a visit to Moscow to discuss the conflict last week, Kerry said that the US was "not seeking regime change" in Syria. And he hailed Russia for its "significant contribution" to efforts to end the war.