Armenia said Wednesday that more than a third of Nagorno-Karabakh's population has fled the enclave since Azerbaijan crushed the rebels' decades-long fight for an independent state last week.
The Armenian government said 42,500 refugees had entered since Azerbaijan lifted its nine-month blockade on the enclave on Sunday.
It added that nearly five thousand more were already en route.
That represents over a third of the region's estimated 120,000 population and marks a fundamental shift in ethnic control of lands that had been disputed by mostly Christian Armenians and predominantly Muslim Azerbaijanis for the past century.
It also adds to the economic strains of Armenia -- a landlocked Caucasus country with few natural resources and emerging problems in its longstanding diplomatic and military partnership with Russia.
The Paris-based support group Armaras accuses Azerbaijan of "ethnic cleansing in the historically Armenian region" of Nagorno Karabakh.
Humanitarian crisis
The Armenian government said it had prepared living arrangements for 40,000 families after last week's fighting broke out.
But Armenian Prime Minister Nikol Pashinyan's spokeswoman said late Tuesday that the government had so far been able to find housing for just 2,850 people.
The looming humanitarian crisis poses a political problem for Pashinyan.
The opposition agreed to end six days of anti-government protests on Tuesday to allow officials to focus on helping the displaced.
Spectre of 1915 Armenian genocide looms over Nagorno-KarabakhDisarming the separatists
Russia is working hand-in-hand with Azerbaijani forces and focused on disarming the separatists under the terms of a ceasefire reached last Wednesday.
The separatists reported the death of 213 people in the one-day fight and Azerbaijan put its toll at 192 soldiers and one civilian killed.
Meanwhile, Azerbaijian authorities say that a total of 192 Azerbaijani troops were killed and 511 were wounded during operations in the enclave.
Moscow is now criticising Pashinyan for his vow Sunday to pivot away from Armenia's longstanding alliance with the Kremlin.
Pashinyan has blamed Russia for failing to avert the Azerbaijani offensive and called Armenia's current foreign security alliances "ineffective" and "insufficient".
Blast
Much of the immediate international aid from organisations such as the Red Cross is being channelled to helping the burn victims of Monday's catastrophic blast.
The explosion happened while hundreds of people were scrambling to get access to the limited supplies of fuel still available in the region after Azerbaijan's blockade.
Azerbaijan waved through about 20 Red Cross ambulances on Tuesday and allowed Armenia to ferry some of the victims by helicopter to a burn clinic in Yerevan.
The blast injured 290 people in all. But officials said on Tuesday that 105 remained unaccounted for and some of the victims were still fighting for their lives.
(With newswires)