Separatist authorities in Nagorno-Karabakh say at least 68 people are dead following an explosion that rocked a fuel depot as thousands fled the region and headed to Armenia.

The blast happened late Monday in the regional capital known as Stepanakert by Armenia and Khankendi by Azerbaijan. Authorities said at least 290 people were hospitalized.

The United Nations' refugee agency said Tuesday the Armenian government reported that some 19,000 people have fled to Armenia from Nagorno-Karabakh since September 23, after Azerbaijan launched an operation to seize control of the area.

'This decades-long conflict, which has flared up again, has displaced many thousands of people,' said Filippo Grandi, the United Nations' high commissioner for refugees, in a UNHCR statement. 'Our teams are on the ground, trying to provide immediate assistance. We need to make sure civilians are protected and humanitarian assistance can reach those in need.'

The United States also will be sending aid to Nagorno-Karabakh, as the White House noted in a statement released Tuesday.

'The United States is announcing additional humanitarian assistance to address health care and other emergency needs, helping local communities provide shelter and essential supplies - such as hygiene kits, blankets, and clothing - to address the needs of those affected or displaced by violence in Nagorno-Karabakh,' National Security Council Spokesperson Adrienne Watson said in a White House statement.

Blast in Nagorno-Karabakh Injures More Than 200 as Thousands Flee to Armenia, Local Official Says

The Nagorno-Karabakh region is entirely within Azerbaijan but had been under ethnic Armenian control since 1994, until parts of it were reclaimed by Azerbaijan during a war in 2020.

Azerbaijan pledged to respect the rights of the ethnic Armenians in the region, but fears of reprisals have pushed many to wait in long lines of cars making their way to Armenia.

Samantha Power, the U.S. Agency for International Development administrator, said Tuesday the Azerbaijan operation made a 'dire situation even worse' for people who were already facing shortages of food, medicine and supplies in Nagorno-Karabakh.

Power told reporters in Kornidzor, Armenia, on Tuesday that it is critical for humanitarian organizations and independent monitors to be granted access to Nagorno-Karabakh and for the government of Azerbaijan to facilitate evacuations of people who are injured.

Power also announced $11.5 million in U.S. humanitarian assistance, including for food, psychosocial services and efforts to reunite families.

Secretary of State Antony Blinken spoke with Azerbaijan's president, Ilham Aliyev, by telephone Tuesday, with Blinken calling for an end to further hostilities.

'Secretary [Blinken] noted in that call that President Aliyev has said that there will be no further military actions and we expect him to abide by that. He also said that he would accept an observer mission and we would expect him to abide by that.'' State Department spokesperson Matthew Miller told reporters during Tuesday's State Department briefing.

Some information for this report was provided by The Associated Press, Agence France-Presse and Reuters.