The Press Trust of India reported Guru, a member of Jaish-e-Mohammad, was executed at 8 a.m. in the Tihar Prisons complex under closely secretive conditions.
The Times of India reported the hanging was witnessed by a select group of officials, including Home Minister Sushilkumar Shindeknowing.
Guru's plea for mercy, which had been pending since 2006, was rejected by the President Pranab Mukherjee late last month, the newspaper said.
Guru was sentenced to death by the Supreme Court in 2004 after being found guilty of planning the December 2001 Parliament attack carried out by five militants who killed nine people before being killed.
Voice of America reported several rights groups had said Guru did not receive a fair trial.
The network said Indian Kashmir was placed under curfew following the announcement of Guru's execution with thousands of security personnel deployed to enforce it.