The rumbles and tremors rattling Leah Appel's Jerusalem apartment building jolted her from sleep around 1:45 on Sunday morning.

Unbeknownst to her at the time, Iran had just unleashed a barrage of drones and missiles at targets inside Israel in what observers around the world fear could mark a dramatic escalation of regional tensions already at a boiling point due to the ongoing war between Israel and Hamas.

Appel, a Montreal native who moved to Israel with her husband after the Oct. 7 attack on that country, said Iran's weekend offensive was unlike anything she had ever experienced in Canada.

"It felt like 1000 ton weights had been dropped in the apartment above our apartment and our whole room was shaking," she said in a call from Jerusalem.

"I said to (my husband), 'Moshe, what is that?' He opened the window and there was just fire in the sky."

The sound of warning sirens soon prompted the Appels and their two children to grab bags pre-packed with food and clothing and troop down to the apartment's bomb shelter.

While Israeli forces and their allies were intercepting 99 per cent of the roughly 300 projectiles fired at Israeli targets, the Appels and other families in their building huddled together to share supplies and comfort frightened children.

Moshe Appel eventually went out with a few others to look around their neighbourhood. 

By 2:30 a.m., he said the sky was clear and everything was quiet.

Despite the speedy resolution, Moshe Appel said the onslaught from Iran was the most intense incident the family has witnessed since emigrating from Canada nearly three months ago.

"This was a very significant attack," he said. "This was essentially hundreds of drones and missiles, which if we didn't have the defence system that we in Israel had, could potentially cause serious harm."

The offensive came less than two weeks after an airstrike blamed on Israel destroyed Iran's consulate in Syria and killed two Iranian generals.

Moshe Appel said Israel's Iron Dome — the country's anti-missile defence system — made him feel safer in the country's capital than he ever felt in Canada.

Sunday was the first day of the Israeli work week, and in spite of a disruption in sleep, he said life in Jerusalem resumed its usual rhythm without missing a beat.

"Around 8 'o'clock on Sunday morning, people were at the cafés, people were at the park, people got on the bus, they went to work. They were getting ready for Passover, it was just business as usual," he said.

"Well, the siren went off, everything's fine. Now we're OK. It's time to go to work. That's just how it is here."

Leah Appel said her 10-year-old son went back to sleep on a mattress in the building bomb shelter almost as soon as she covered him with a blanket.

"He knew he was safe among his friends," she said. "He slept through it. He woke up this morning, and he went to the park."

The couple's 11-year-old daughter has been following the news closely. She went to bed dressed and had an emergency bag packed so she could get up and leave immediately.

The Appels said they "really hope" Iran's offensive marks the worst of things and tensions start to subside. 

They described the attack as "frustrating and said it could've destroyed holy sites that are important to Muslims, Christians and Jews alike. 

"My understanding is that Israel wants to retaliate. The world at large is just sort of telling us not to. I'm not sure about the wisdom one way or the other," Leah Appel said. 

"If we don't retaliate, it gives (Israel's enemies) a chance to sort of rebuild and try to attack us again. If we do retaliate, it can sort of drag our resources away from the things that we're concentrating on now. I feel like it's probably not good, either way, because you don't really want a war. Right? Nobody ever wants a war."

Back in Canada on Sunday, the Iranian attack ushered in a long night of mixed emotions for Francis Weil. The president of the Moncton Jewish Community watched the unfolding drama on TV from his home in New Brunswick and fielded dozens of messages from those who feared the assault would cause harm.

But Weil said he had "confidence" Israel had the systems in place to hold the attack at bay. 

"My reaction is mainly that why did Iran not realize that they were just wasting their time and their money shooting at Israel," he said. "For me, it was quite obvious that the thing would not succeed."

In Tehran, meanwhile, news of Iran's offensive came as a surprise to Alireza Ghandchi.

The Richmond Hill, Ont., resident, who is visiting his parents in the Iranian capital for Ramadan, said most people there don't see the point of launching such an attack. He described the effort as more of a display of power and a show of might rather than anything substantial. 

Still, he recognized in an interview the attack could well trigger retaliation from Israel. A key minister in the country's war cabinet said Sunday Israel would "collect the price from Iran, in the way and at the time that suits us.”

The mood in Tehran is one of fear, Ghandchi said, adding residents worry an attack could come at night. 

"The people are tense and they are worried ... I hope things calm down."

– Hina Alam, The Canadian Press

With files from The Associated Press