KYIV, May 18 - Nearly 1,000 last-ditch Ukrainian fighters who had held out inside Mariupol’s pulverized steel plant have surrendered, Russia said Wednesday, as the battle that turned the city into a worldwide symbol of defiance and suffering drew toward a close.

The Ukrainian fighters who emerged from the ruined Azovstal steelworks after being ordered by their military to abandon the last stronghold of resistance in the now-flattened port city face an uncertain fate, The Associated Press reported. Some were taken by the Russians to a former penal colony in territory controlled by Moscow-backed separatists.

While Ukraine said it hopes to get the soldiers back in a prisoner swap, Russia threatened to put some of them on trial for war crimes.

Amnesty International said the Red Cross should be given immediate access to the fighters. Denis Krivosheev, Amnesty’s deputy director for the region, cited lawless executions allegedly carried out by Russian forces in Ukraine and said the Azovstal defenders “must not meet the same fate.”

It was unclear how many fighters remained inside the plant’s labyrinth of tunnels and bunkers, where 2,000 were believed to be holed up at one point. A separatist leader in the region said no top commanders had emerged from the steelworks.

The plant was the only thing standing in the way of Russia declaring the full capture of Mariupol. Its fall would make Mariupol the biggest Ukrainian city to be taken by Moscow’s forces, giving a boost to Putin in a war where many of his plans have gone awry.

Military analysts, though, said the city’s capture at this point would hold more symbolic importance than anything else, since Mariupol is already effectively under Moscow’s control and most of the Russian forces that were tied down by the drawn-out fighting have already left.

Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said 959 Ukrainian troops have abandoned the stronghold since they started coming out Monday.

Video showed the fighters carrying out their wounded on stretchers and undergoing pat-down searches before being taken away on buses escorted by military vehicles bearing the pro-Kremlin “Z” sign.

The U.S. has gathered intelligence that shows some Russian officials have become concerned that Kremlin forces in Mariupol are carrying out abuses, including beating and electrocuting city officials and robbing homes, according to a U.S official familiar with the findings.

The Russian officials are concerned that the abuses will further inspire residents to resist the occupation and that the treatment runs counter to Russia’s claims that its military has liberated Russian speakers, according to the official, who was not authorized to comment. (om/ez)