When an Israeli airstrike targeted a security office near her home in Gaza this month, 10-year-old Zeina Dabous frantically scribbled a note and slipped it under her mother's pillow.

"Mummy, my love, I am very very scared. If we all die, put us in the same grave all together so I can stay in your arms," she wrote.

"I want to wear my eid clothes," she added, of the outfit she never got to wear for the Muslim celebration after Israeli airstrikes on the Palestinian enclave started on May 10.

The 11-day bombing campaign came in response to rocket fire from Gaza by Hamas and other militants, triggered by an Israeli forces crackdown on worshippers at East Jerusalem's Al Aqsa Mosque compound.

Though a ceasefire has since Friday halted the air raids, experts warn that children in the besieged coastal strip will likely carry the mental scars for years to come.

Psychologists say many are showing signs of depression, anxiety, behavioural disorders or irritability and many are wetting their bed.

At home in Gaza city just before the bombing stopped, Zeina said she was constantly petrified and barely sleeping.

"They're always bombing," she told AFP.

After a strike hit very close, "before sleeping I wrote a note in red pen to my mother and slipped it under the pillow because I was scared I would die", she said.

Zeina is one of around a million children living in Gaza, according to the UN's children agency UNICEF.

Israeli strikes on Gaza killed 248 Palestinians, including 66 children, and have wounded another 1,900 people, the Gaza health ministry says.

Rockets and other fire from Gaza have claimed 12 lives in Israel, including one child and an Arab-Israeli teenager, an Israeli soldier, one Indian, and two Thai nationals, medics say. Some 357 people in Israel have been wounded.

There is controversy about how many of those killed in Gaza were combatants, and how many were civilians.

Israel's Prime Minister Benjamin Netanyahu said Israel's bombing campaign had killed "more than 200 terrorists" in Gaza.

'Don't be scared' 

Israeli air strikes also pounded the densely populated enclave in 2008-2009, 2012 and 2014.

When the last war raged, Zeina was no older than four.

"A whole generation of children has been ravaged by repeated conflicts,” said Zeina’s grandfather, Saeed Dabous.

The charity Save the Children on Friday warned that children in Gaza would suffer for years to come.

They "are suffering from fear and anxiety, a lack of sleep, and are displaying worrying signs of distress, such as constant shaking and bedwetting”, it said.

In their grandfather’s home, Maysa Abu al-Awf, 22, held her two-year-old brother Ahmad on her lap and tried to comfort him after they lost two sisters and dozens of relatives in a devastating air strike.

"I’m scared, I’m scared,” Ahmad constantly repeated, a scab on his hand and stitches on his bare foot.

Maysa said that whenever he heard an explosion, he cried out. "I tell him, ‘don’t be scared, it’s just the sound of balloons popping’.”

After air strikes demolished their four-storey family home in Gaza city on Sunday last week, Maysa, little Ahmad and their sister Maram, who is seven, screamed for hours under the rubble before they were rescued.

Their two sisters, 20-year-old dentistry student Shaima and 17-year-old school pupil Rawan, did not survive.

Sitting beside her grandfather, Maram shook as she recounted being trapped under the rubble.

"I called out for Mummy... I called for them to get me out,” she said.

At the site of her demolished home, AFP saw Maram’s favourite red teddy bear lying in the debris, foam spilling from its left leg.

"I am sad,” Maram said. "All my books and notebooks were burnt.”

‘Catastrophic number’ 

In the Gaza Strip’s main Shifa hospital, their 16-year-old cousin Omar was in shock after the same strike killed his two brothers and father, who was the head of internal medicine at the facility.

He had stopped talking, his family said.

During Israel’s latest military campaign on the coastal strip, which is home to two million people, the Gaza Community Mental Health Programme (GCMHP) posted advice for parents on Facebook.

It told them to discuss feelings with their children, but also to try to distract them from the sounds of war with games, drawing or prayers.

There is no overall tally of how many children are suffering from mental health issues in Gaza due to repeated conflict, the GCMHP says.

But it said it records hundreds of new cases a month.

Psychologist Mohammed Abu Sabeh said children exposed to "great trauma” often then exhibit "violent behavioural disorders”.

"The wars are sowing violence in schools and homes,” he said.

Most children in the Gaza Strip suffer from "depression, anxiety or a behavioural disorder”, and "a catastrophic number” of them need treatment.

"I’m not optimistic,” Abu Sabeh said.

"This war will create an aggressive, violent and hateful generation.”