Firial Sabur was born five months ago. He doesn't yet know that he has already lost his father. Omar Sabur died on Wednesday after he was shot by a sniper. When Sabur's brother Abdala tried to rescue him, he too was shot dead. On Friday, the baby was dozing in his mother's arms, unaware of the chaotic scenes around him in the only bomb shelter in Baba Amr.

The word "shelter" is an exaggeration: close to a year ago, the shelter was a basement used for wedding parties. Chinese paper lanterns and few paper flowers still hang from the ceiling. There are still hookah pipes. But the parties have long gone and a storm of shrapnel and bullets threatens to cut off this underground room where 220 people, mostly women and children, have sought shelter.

To reach the bunker, you must wait until nightfall. It is the only time that brings some kind of calm to the neighbourhood, when the systematic bombardment comes to an end and the drones that seem to guide the attacks are no longer flying.

Under the cover of darkness, Baba Amr wakes up; its inhabitants emerge into rubble-filled streets. They hurry to salvage what they can and move across the Homs district in cars riddled with bullet holes. It is also the time when you can see the Free Syrian Army moving ammunition up towards the frontline.

Only then can you truly realise the extent of the devastation the enclave has suffered: not a single street has escaped shelling. A drive through the neighbourhood is a journey though sheer ruin.

Many of the houses have been abandoned after being targeted repeatedly by rockets and shells. The shelling is what brought Firial and the others to the shelter, where they gather in family groups, dozing on mattresses.

The women cook for everyone – or rather they improvise. Yesterday there was rice. "A week ago there was no bread. The last delivery was inedible," says Abu Harb, Firial's uncle.

As he speaks, shooting from government snipers can be heard in the background. Even at night, the hunters of human beings are on the lookout and the only way to cross the road is by running.

"We have been buried alive. I feel as if I am in prison," says Harb, 29.

One man, Abu Ahmed, says he has been 20 days without seeing daylight. Only a few dare to leave the refuge – even at night. Last week, two of the residents were injured by a shell in the doorway of the shelter.

The punishment that Homs has taken has brought hardship upon hardship to its inhabitants: Ahmed lost his house in a missile strike. In April he lost a leg when a soldier shot him in the knee and the wound turned gangrenous.

Not far from his mattress lies another amputee who shows the stump left when a rocket-propelled grenade exploded in his house. "Look me in the eyes. I am 56 but I look 100 years old. This place is smothering me," he says.

Dozens of children crowd around a visitor – perhaps one of the only novelties in their life in the shadows. There is no electricity here.

"The children wet themselves from fear. Others wake up with nightmares," says Abu Nida. The 25-year old ended up in the shelter after twice evading death. His family's home was hit by a missile. They moved to another house, and a few days later it was also hit. He has been in the refuge for 19 days.

Rim, his two-year-old daughter, clings to his legs when the explosions intensify. "She says, 'I'm very scared, Daddy.' And I tell her, 'Don't be afraid – say Allahu Akbar [God is great].'"

The inhabitants of Baba Amr – a few more than 20,000 before the offensive – know their daily routine well. The artillery barrages start early, before 7am. After that, going on to the street is suicidal. Those who do run like someone possessed and hide in doorways every time they hear a blast from shellfire.

Only people like Ahmed Abu Leila, who fought the Americans in Iraq, dare to say they are happy. "We prefer to live like this and be free than to live like we did before," says the 28-year-old.

He always carries his "girlfriend" – a Kalashnikov assault rifle – and sometimes an anti-tank rocket as well.

Abu Leila says he belongs to one of the more fearless group of fighters from the Free Syrian Army. They fight in Yakura, the most exposed frontline in Baba Amr – and one of the entry points to the neighbourhood that President Bashar al-Assad's army is trying to take. They call themselves al-Mukatilun al-Tayarun, "the flying fighters".

"This area has been so heavily bombarded that lots of the boys have been sent flying. They get up, give themselves a couple of slaps to wake up, and they carry on fighting," says fellow fighter Wael.

"This is a very dangerous street: we have to run across one at a time," Abu Leila says during a night-time tour of Baba Amr. Despite the relative calm that comes with darkness, government troops and Free Syrian Army fighters are still exchanging fire somewhere nearby. A few bullets whistle overhead, forcing us to take cover.

Abu Mohamed, a doctor at the ramshackle local hospital, has not lost a grim sense of humour. He says that the clinic is a kind of "garage for minor breakdowns". Wounded patients arrive, are bandaged up and then are sent home. "The ones with serious injuries die. We don't have any way to save them," he says.

Diar Abu Salah was one of them: a sniper's bullet hit him in the stomach. All the doctors can do for him is to declare him dead. A few minutes later, a truck arrives to take away his body – space must be made, because the stream of new victims is unending.

In another room, Mohamed, a one-year old boy, cries inconsolably. He was hit in the forehead by a fragment from a shell. "Mother! Mother!" he wails, clinging to his milk bottle.

"Is he a terrorist?" his older brother asks, pointing to the infant.

All I can do is bow my head and carry on taking notes.

Javier Espinosa is Middle East correspondent for El Mundo newspaper