Vodafone is the largest mobile provider in eastern Ukraine but its fibre optic line was cut. The company says it needs reassurances from the warring parties to repair the damage.
Almost two million people lost mobile phone access in war-torn eastern Ukraine after the last major provider in the devastated region suffered a fibre optic line cut.
Vodafone Ukraine said on Tuesday it could not say how long it would take to restore service because its workers had not received security assurances from the warring parties in a conflict that has claimed more than 10,000 lives in nearly four years.
A deliberate act?
Vodafone said it had appealed to the Kiev authorities and monitors from the Organization for Security and Cooperation in Europe (OSCE) to guarantee safe access to its repair crews.
"It has been futile so far," Vodafone spokeswoman Viktoria Ruban wrote on Facebook.
The head of the self-proclaimed and Russia-backed Donetsk People's Republic accused Kiev of deliberately cutting the phone link as part of its "information warfare".
"Kiev has halted Vodafone's work on the territory of the Donetsk People's Republic," Alexander Zakharchenko said.
The outage has all but cut communication between family members living on opposite sides of the frontline splitting eastern Ukraine.
The two remaining mobile phone carriers are operated by the Russian-backed authorities.
The one in Donetsk called Phoenix only this week introduced a service that is theoretically able to place calls to Kiev-controlled regions at international rates.
These are comparatively high - $0.18 (15 euro cents) a minute - and a burden for people living in one of the poorest corners of Europe.
The departure of Ukraine's KyivStar in 2015 and Lifecell last year left Vodafone as the only major provider in the region of some 3.5 million people.
This has left Phoenix filling the void in Donetsk.
But it has only 600,000 subscribers and is already operating at full capacity.
"The more people join Phoenix, the worse it works," said Viktoria, a 19-year-old student.
Donetsk "communications minister" Viktor Yashchenko told the separatist DAN news agency that 80,000 people had joined Phoenix since Vodafone went down.
Many queueing to sign up for the insurgent operator expressed their resentment on Tuesday.
"We have slipped back into the Stone Age," said Alexander, a 29-year-old engineer, as he waited to purchase a Phoenix phone card.