MOSCOW — Some of the Russian troops massed near the Ukrainian border began to pullback Friday, a possible step toward de-escalating tensions in the region after the military buildup had raised international alarm.

Russia released video of troops who had been involved in exercises in Crimea loading onto ships, planes and trains for a return to their home bases. On Thursday, Defense Minister Sergei Shoigu ordered the military withdrawal, saying it should be completed by May 1.

But it remains unclear how many forces will remain and what military infrastructure will stay in place near eastern Ukraine, where pro-Moscow rebels have battled Ukraine’s Western-allied government for seven years.

In his state-of-the-nation speech on Wednesday, Russian President Vladimir Putin didn’t address why Russia had deployed additional forces to the eastern Ukraine border and the Crimean Peninsula.

But Russia’s military surge into the region — including the Crimea Peninsula that was annexed from Ukraine in 2014 — was widely seen as a warning to the Biden administration and allies that Moscow stands firmly behind the eastern Ukraine separatists and its hold on Crimea.

“I hope no one will cross the red line in regards to Russia,” Putin said Wednesday. “And where this red line will be drawn, we will decide for ourselves.”

Michael Kofman, a senior researcher at the CNA think tank who has been monitoring the military activity, said on Twitter that he “would not count the matter resolved.”

The pullback is partial. For example, armored vehicles at one field camp in the Russian region of Voronezh, about 100 miles from the Ukraine border, are staying put.

“The next two weeks will prove telling,” Kofman said. “If Russia actually begins to redeploy as suggested, then it is fair to interpret this affair as a coercive demonstration, but it also appears that some elements will remain. How much, where, and for how long — these are outstanding questions.”

The conflict between Russia and Ukraine has been a major rift between Moscow and the West, and Russia’s annexation of Crimea prompted international condemnation and sanctions.

Estimates of some 85,000 to 110,000 Russian troops massed at the border had stoked fears in Ukraine and the West that Russia was preparing to annex the separatist-controlled region.

Analysts have said Russia’s objective for the buildup may have been to send a message to Ukrainian President Volodymyr Zelensky not to attempt to change the status quo in the region because of a new U.S. administration that has vowed to take a harder line with Moscow.

State Department spokesman Ned Price told journalists Thursday that Russia’s troop pullback had been noted and the United States will “be watching closely for that follow through.”

Zelensky wrote on Twitter that “the reduction of troops on our border proportionally reduces tension. [Ukraine] is always vigilant, yet welcomes any steps to decrease the military presence and de-escalate the situation in Donbas. Ukraine seeks peace.”