Sonalisa Nag woke up at 5.30am on Friday to her daughter Salona's message on WhatsApp: "Don't worry. I am fine."

Instead of calming her down, the message got her more worried because several calls to Salona's phone went unanswered.

"When we did not get her on the phone, we got worked up," her father Pradeep Nag said.

Meanwhile, they got to know about the Nice terror attack from TV news.

"We thought she might be sleeping but we kept worrying about her till the time we spoke to her," he said while speaking to Metro at their Golf Green home on Friday evening."

Around 11am, the Nags were relieved when Salona called to say she was safe in her studio apartment in Valrose. Her place is a 20-minute tram ride from the Promenade des Anglais where a truck ploughed into a crowd during the Bastille Day celebrations on Thursday night, killing 84 people.

"Only when we heard her voice, did our tension dissipate," Nag said. "Till the time we spoke to her, we were worried about her safety."

For the Nags, the worry is not new. The family had spent tense moments during the Paris attack in November as their elder daughter Lipsa was doing her research in the French capital.

Lipsa still lives in Paris and on Thursday night she was at the Champ de Mars near Eiffel Tower to see the fireworks. She's been living in Paris for three years.

"My wife and I have been discussing why we chose France when it seems to be such an easy target," Nag said. "But we have to accept this because they cannot give up their careers at this stage."

Salona went to the French city of Lyon in August to do an MBA. She's been interning at Nice since May and will stay there till September.

"When we spoke to Salona, she sounded calm. She said Nice was returning to a semblance of normality," Nag said.