DAMASCUS (Reuters) - Damascus residents were woken before dawn on Saturday by a series of explosions resounding across the city, very loud even for people used to the sound of heavy bombardment.

Ten hours after the missiles hit, smoke was still rising from the remains of a research facility in Damascus’s Barzeh district that Western countries say was part of a covert Syrian government chemical weapons program.

The United States, Britain and France attacked sites across Syria in response to a suspected poison gas attack a week ago, but the Syrian government, backed by Russia, denies using - or possessing - any such weapons.

The blasts left the Syrian Scientific Research Centre compound, standing hard against the steep, dry hills that hem in northeastern Damascus, little more than a ruin.

The center is not far from eastern Ghouta, the area of towns and farmland that was the biggest stronghold of rebels fighting President Bashar al-Assad. The last group of them surrendered hours after the suspected chemical weapons attack that prompted Saturday’s air strikes, at the end of a government offensive on the region that had lasted seven weeks.

Standing near the rubble, Saeid Saeid, head of the center’s polymers department, said that the buildings had been used to research and make medicine components that could not be imported, including ones for cancer treatment and anti-venom.

U.S. Marine General Joseph Dunford, chairman of the joint chiefs of staff, said in Washington that it had been a center for research, development, production and testing of chemical and biological weapons.

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Pentagon spokesman Lieutenant General Kenneth McKenzie said that 76 missiles had been fired at the facility and “successfully destroyed three buildings in metropolitan Damascus, one of the most heavily defended aerospace areas in the world”.

The smell of fire and smoke wafted across the remains of five destroyed buildings during a media tour arranged by the government. Only the compound’s gateways and one heavily damaged building survived.

Other buildings were mostly flattened, some with a corner still upright, the slabs of concrete that had once been roofs or floors hanging at odd angles.

A bus parked nearby was little more than a skeleton, its windows blown out. Palm trees looked ragged, as if they had lost some of their fronds.

Amid the rubble on the edge of the compound were the scattered remains of its contents: charred books, laboratory masks and gloves, files, tables, cardboard packets marked with the names of medicines, chairs and wind-blown sheets of paper.

Scraps of green and white lab coats hung from the branches of trees, blown there by the blast or later on by the wind.