BEIRUT, Lebanon — With the Syrian rebel enclave of eastern Aleppo shriveling, Russia said on Monday that it would start talks with the United States this week on a deal for holdout insurgents to leave, and that any who refused would be regarded as terrorists subject to deadly assault.
There was no immediate comment from the United States on the Russia announcement, conveyed by Foreign Minister Sergey V. Lavrov at a news conference in Moscow. But such an agreement with the United States, which has supported some of the insurgents ensconced in Aleppo, would appear to constitute a shift in American policy.
United States officials, as well as the special United Nations envoy for Syria, Staffan de Mistura, have up to now called only for a deal to evacuate several hundred Qaeda-linked fighters, not all the insurgents, who are believed to number several thousand.
Mr. Lavrov’s comments came during another terrifying day for civilians in Aleppo, the formerly vibrant commercial epicenter of Syria that has become a pivotal battleground in the nearly six-year-old Syria war.
Two Russian nurses in Aleppo were killed when mortar rounds apparently fired by rebels hit a hospital, prompting calls from Syrian government supporters for Russia to escalate its involvement in the battle.
In the shrinking rebel redoubt on the eastern side of the city, intense artillery shelling and airstrikes forced residents to cower in basements. Some barrages were striking at the rate of a shell every second, some residents reported via text message, transmitting what appeared to be audio recordings of the blasts.
It was unclear how many people were killed in the Monday barrages, as makeshift health care systems in eastern Aleppo collapsed, but residents described seeing bodies on the streets because no one could pick them up.
On the government side, eight people were killed by rebel shelling on Monday, state media reported.
Russia news media said the two nurses were killed from shelling on an Aleppo park that had been turned by the army into an field hospital. They were among the most high-profile deaths of Russian military personnel assisting the government of President Bashar al-Assad.
Russia’s military assistance has been crucial to keeping the government afloat, and it has been providing food and services to people fleeing eastern Aleppo in the recent fighting, even as it is blamed by the opposition for backing indiscriminate bombing by the government.
Mr. Lavrov said he was confident that an agreement would be reached with the United States on a rebel withdrawal in talks to be held in Geneva starting on Tuesday or Wednesday.
He said Secretary of State John F. Kerry had submitted a proposal for the routes and timing of the fighters’ departure after meeting Mr. Lavrov in Rome on Saturday.
“Those armed groups who refuse to leave eastern Aleppo will be regarded as terrorists,” Mr. Lavrov told reporters. “We will treat them as such, as terrorists, as extremists and will support a Syrian army operation against those criminal squads.”
Perhaps one indication of the intensification of violence on Monday was that nearly every person contacted in Aleppo had been injured or experienced a scare.
In one part of rebel-held Aleppo, Hisham Skeif, a local council member, had been wounded in his hand by shrapnel. Bassem Ayoub, an antigovernment activist, survived a nearby shelling that damaged his car. Zaher al-Zaher, another activist, said he was walking with his mother when a shell fell seven meters away.
“No words can describe the situation. The shelling is not only close but they’re falling on us,” he said.
A government maintenance worker on the western, government-held side heard heavy shelling and saw smoke nearby, and said his sister had been wounded in the hand by shrapnel in another area.
Shells also fell in the area of Aleppo’s Shahba hotel, according to several international journalists staying there. A Russian journalist was reported injured in the field hospital shelling.