KIEV, Ukraine — Russia’s withdrawal of troops from its border with Ukraine has eased fears in Ukraine and the West that President Vladimir Putin will launch a full-scale invasion.

But the risk of war has not receded, only shifted. Daily clashes, one involving 300 armed separatists attacking a border post, signal the conflict has moved into a higher gear.

Ukrainian officials charge that Russia is training, arming and dispatching irregular forces, many of them Russians, including a surprising number of Chechens, to the troubled eastern region to keep Ukraine permanently destabilized.

“They are sending in an irregular army,” said Anton Gerashenko, spokesman for the Ukrainian Interior Ministry. “They want this to become another Somalia.”

Perhaps the best proof of this was that at least eight of the rebels killed in the battle over Donetsk airport Monday and Tuesday were put in red coffins and taken to Russia for burial, Gerashenko said.

Denis Pusilin, head of the high council of the so-called Donetsk People’s Republic, had put the number higher, saying 34 felled militants were taken to Russia for burial.

The new phase in the war began just after the assault on the airport, when Pusilin sent a public plea to Putin to send in military help.

That night, a convoy of cars and vans approached one border crossing, where border guards engaged in a firefight and blocked them. But at another point, some 40 truckloads of armed insurgents made it in, allowing as many as 1,000 militants to cross in. Guards were apparently bribed to open the gates.

That number is “about right,” said Egor Pavlovich Firsov, a member of Parliament from Donetsk, the biggest city in eastern Ukraine.

The biggest clash occurred Thursday, when border police reported that nearly 300 militants stormed a border crossing at Stanychno, northeast of Luhansk, firing rocket-propelled grenades and small weapons.

On Friday, about 80 militants, equipped with mortars, rocket-propelled grenades and small arms attacked a border post at Dyakovo, about 50 miles south of Luhansk, firing some 50 mortar rounds, wounding three, one seriously, border police said.

There were other signs of Russian involvement. On Wednesday, Ukrainian forces downed an unmanned Russian-made surveillance drone over one of their checkpoints. The drone is capable of providing 3-dimensional maps, a sign Russia is willing to provide advanced technology to the rebel movement.

On Thursday, rebel forces shot down an Mi-8 helicopter near Slovyansk, the epicenter of the conflict, killing a major-general in the Ukrainian National Guard and elite servicemen and five others, and bringing to more than 50 the number of soldiers and officers killed since mid-April.

Russia is not the only source of discord. Ukrainian government officials said they believe the country’s richest oligarch, industrialist Rinat Akhmetov, who had been credited with stanching separatist sentiment just two weeks ago, may have switched sides again and now is working with one of the anti-government armed factions.

Akhmetov had been widely credited with easing tensions by urging his 300,000 employees to join him in opposing the “Donetsk People’s Republic,” which he said was “in a fight against our region.” But after leaders of the DPR threatened to nationalize his holdings and sent a mob to attack his residence in Donetsk on Tuesday, he shifted his position again.

“I know that last Sunday, when they went to destroy the Akhmetov residence, he paid a lot of money to terrorists not to do it,” a senior security official said on condition of anonymity. He said the beneficiaries of Akhmetov’s payment were the “Vostok” separatists’ battalion, which is under the command of Russian-born Igor Girkin, whom the government here says is an officer of the Russian GRU intelligence service.

On Tuesday, the Vostok battalion seized control of the 11-story regional administration building from the ragtag group of pro-Russian separatists who had been occupying it. That, too, was at the demand of Akhmetov, said the senior Ukrainian official.

“He did it to show that he can do something,” the official said. “So he bought one group of terrorists to battle other terrorists.”

After the building came under Girkin’s control, the “People’s Republic” announced it was establishing a government, and named Girkin as its defense minister.

The government in Kiev appears to be deeply troubled by Akhmetov’s apparent flip-flops. The senior security official said the wealthy businessman was moving to protect his business interests. “About 30 percent of his business is with Russia,” the official said.

Neither Akhmetov nor his spokesman would comment on the government allegations.