Israeli raids on a Syrian military facility interrupted the quiet of night, causing the ground to shudder and turning the black sky red, witnesses said on Sunday.
"It was like an earthquake, the sky was yellow and red," said 72-year-old Najwa, a resident of the Dumar district of Damascus, about six kilometres (four miles) from the site of the raids.
"The explosions went on for around four hours, they were incredibly powerful," she added, saying they could be heard far from the scene of the attack.
State media said the strikes hit a military research facility at Jamraya in the Eastern Gouta region that lies between the capital and Lebanon.
The reports accused Israel of carrying out the raids, but did not provide any other details on casualties or damage caused.
Video footage of the strikes uploaded to YouTube showed a series of missiles lighting up the clouds overhanging Mount Qasiun as they head towards their targets.
A fire started by the raids is seen burning, captured on camera from a distance, and then suddenly an enormous explosion erupts, producing an orange fireball that momentarily fills the entire screen.
The powerful explosion sent up towering clouds of smoke illuminated by embers of debris and a least one small blast can be heard subsequently.
Bassam, a 60-year-old teacher also living in Dumar, said the blasts began about 3:00 am (0000 GMT).
"A huge explosion woke us up. The whole building shook. That was followed by a series of explosions that lasted for half an hour and kept us awake."
"I've never experienced such horror. We heard really loud explosions. We felt as thought the bombing was targeting our house," said Salwa, 50, another Dumar resident.
"We hid in the corridor of the house," she added.
The Syrian Observatory for Human Rights watchdog, which relies on a network of activists, doctors and lawyers on the ground, reported deaths in the blast, but there was no official confirmation.
"Residents of Qudsaya, a suburb northwest of Damascus, said they saw aircraft at the moment when the explosions took place at the Jamraya research centre," the group said.
"The rebels do not have the means to produce an explosion of that force," added the Britain-based group.