The sender of the invitation was a boy studying in Class 9 in Bhilwara district, an Anti-Terrorist Squad officer said.
"His father was not (available) today, hence he was not called for questioning. He is likely to be questioned tomorrow," the officer said.
The police said they have registered a case in this connection after a youth reported to them that he has received the invitation on WhatsApp from the group named "Lashkar-e-Toiba".
"When the members of the group clicked on the invitation link, there was nothing. An FIR has been registered against the sender of the invitation under sections of the IPC and the IT Act. We have also informed the UP Anti-Terrorist Squad," Lucknow cyber-crime cell nodal officer Abhay Mishra said.
When contacted, IG (ATS) Asim Arun told PTI that it was not yet clear whether the youth joined the LeT group or not.
"But he informed the police, and the number from which the invitation had come was tracked. It was found the invitation had come from Bhilwara district of Rajasthan," Arun said.
"We are working with the Rajasthan Police on this case," he added.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.