A mother of seven accused of treason for telling the Ukrainian embassy about Russian troop movements was to be released from jail Tuesday, her husband said, though the charges against her remain.

Svetlana Davydova, who faces between 12 and 20 years in prison, is being held in the high-security Lefortovo jail in Moscow. 

Fears grew Tuesday of an escalation in the mounting bloodshed in east Ukraine as the United States mulled arming Kiev and pro-Russian rebels ordered a mass mobilization.

At least 16 civilians and five government troops were killed over the past 24 hours in fierce clashes across the conflict zone, government and pro-Russian rebel officials said.

Washington is once again mulling military support to Ukraine after fierce offensives by Kremlin-backed rebels, but experts fear it will only justify Russian conspiracy theories and drive East and West closer to full-blown war.

The recent rebel attacks across key parts of the frontline in eastern Ukraine may have been timed precisely out of fear the United States could soon get involved.

A mass call-up Monday by separatist authorities aimed at boosting their forces in east Ukraine to 100,000 fighters sparked mixed reactions from inhabitants in rebel bastion Donetsk.

While some met the call-to-arms -- which the pro-Russian rebels said was voluntary -- with jingoistic fervor, others who spoke to Agence France-Presse dismissed the plan as fantastical or said they had no intention of signing up.

Germany will not provide Ukraine with weapons to fight Russian-backed rebels in the east, Chancellor Angela Merkel said Monday, stressing the need for a diplomatic solution to the conflict.

"Germany will not support Ukraine with guns and weapons," Merkel said at a press conference after meeting Hungarian Prime Minister Viktor Orban in Budapest.

Russian conscripts are coming under new pressure to sign up as professional soldiers and fear being dispatched to fight in Ukraine alongside Moscow-backed separatists, rights activists said Monday.

Activists sounded the alarm after a new spike in complaints from recruits doing compulsory military service and their families, as peace talks have broken down and fresh fighting is erupting in eastern Ukraine.

A Dutch team recovered more body parts at the MH17 crash site in war-torn Ukraine, where 298 were killed when a Malaysia Airlines jetliner crashed in July, officials said Monday.

"They recovered a small amount of human remains of the victims," Dutch defense ministry spokeswoman Marloes Visser said.

Pro-Russian separatists vowed Monday to mobilize up to 100,000 fighters for their latest east Ukraine offensive as the United States mulled sending weapons to Kiev's outgunned forces after the latest truce bid collapsed.

The pledge to dramatically escalate a nine-month conflict that has already left at least 5,100 people dead came as the rebels battled to encircle the beleaguered transport hub of Debaltseve.

NATO's military commander and Obama administration officials appear to be moving toward supporting sending defensive weapons to Kiev's forces fighting pro-Russian separatists in eastern Ukraine, The New York Times reported Sunday.

Though President Barack Obama has not yet decided whether to send "lethal assistance," his administration is reviewing the issue after a surge in fighting between Kiev and Kremlin-backed rebels, the Times reported.

Camping out for now at a children's holiday camp in the east Ukrainian town of Svyatogirsk, Oleksandr Khodor tots up everything he was forced to leave behind.

"In one fell swoop, I lost everything," Khodor, 34, told AFP.