A 20-year-old Ngee Ann Polytechnic graduate in Europe on a graduation trip with four of her fellow graduates was just 400m away when a truck ploughed through a crowd outside a department store in central Stockholm, killing four people and injuring 15.

Ms Nuruljannah Mohammad Razib was a few blocks away from the corner of the Ahlens department store and popular pedestrian street Drottninggatan when the attack happened on Friday.

Ms Nuruljannah, who is on her way to Finland, told The Sunday Times via WhatsApp yesterday that she did not see the actual attack but saw people running away from the site.

"We were shocked and shaken," she said. "We were told to clear out of the area. While walking in the streets we saw soldiers and policemen with guns on the streets and also many ambulances."

Her father Mohammad Razib, 48, had contacted The Sunday Times on Facebook yesterday to remind Singaporeans to stay in touch with family members who are travelling and for travellers to register with the Ministry of Foreign Affairs (MFA).

He said he and his wife had just finished a Facetime chat with his daughter, the second of his three children, when she sent a message at 10.11pm on Friday: "Something happened near where I was. An accident/attack. A car drove into a shopping mall near the MRT station my friends and I were at. It happened 400m away from us. Now the city area is being evacuated."

She and her friends, all nursing diploma graduates, had been shopping in the area but Ms Nuruljannah and another friend were closest to the attack.

They had to walk 5km to be picked up by a friend's uncle, who took the girls to his home. The city was in lockdown mode.

Mr Raziband his family were in constant communication with his daughter via WhatsApp for updates.

Ms Nuruljannah and her friends have been travelling to various countries in Europe including France, Germany and Italy, and Finland is their last stop.

Mr Razib said: "We want to share the importance of constant communication with loved ones abroad, considering threats such as this are rampant."

He said the girls probably registered with the MFA before they went on their Europe trip.

"It is important to know that our own country, our own government has planned education and awareness that while (attacks like) this may not affect us here closely, it is only a matter of time and inevitable," said Mr Razib.

Ms Nuruljannah said the experience taught her what to do and not to panic, and to be more aware of her surroundings.

"We may never know when any attack can happen, even in Singapore," she said.