New Delhi, May 12 (IANS) At least 21 addresses, including four hospitals in the national capital, received bomb threats through email on Sunday, sources said, adding that searches were underway on the premises of all four medical facilities.

Burari Government Hospital, Sanjay Gandhi Hospital in Mangolpuri, Superspeciality Hospital in Janakpuri, and Hindu Rao Hospital on Sunday afternoon received bomb threat emails.

"I have placed explosives inside the building. They will explode... this isn't a threat, you have a few hours to defuse the bombs or else the blood of innocent people inside the building will be on your hands," read the email whose screenshot was accessed by .

"The group called 'Court' is behind this massacre," the email sent around 3.05 p.m. on Sunday read.

"An email was received at the Burari Government Hospital regarding a bomb threat. Nothing suspicious has been found yet," Deputy Commissioner of Police (North) Manoj Kumar Meena said.

Police personnel along with bomb disposal teams and sniffer dogs rushed to the hospitals.

"The Fire Department and other relevant departments were also informed about the emails to the hospitals," said another police officer, adding that searches were underway.

The fresh threats have come days after over 100 schools received bomb threats via email in the national capital.