Indian Prime Minister Narendra Modi addresses his Bharatiya Janata Party's campaign rally in support of East Delhi candidates ahead of Delhi state elections in Delhi, India, Feb. 3, 2020. (Xinhua/Partha Sarkar)

India tightened public security on Wednesday after the circulation of a letter warning of Islamist militant attacks to avenge derogatory remarks about the Prophet Mohammad by an official of the ruling Hindu nationalist party.

Several Indian media groups shared the June 6 letter attributed to al Qaeda's branch in the Indian subcontinent (AQIS) in which threats were made to carry out suicide bombings in Indian states to defend, it said, the honor of the Prophet.

"We have also ordered state police to ensure public gatherings or protests are not allowed as they could be targeted by the militant group," a senior home ministry official in New Delhi said.

The security threat surfaced days after a spokeswoman for Prime Minister Narendra Modi's Bharatiya Janata Party (BJP) made comments about the Prophet Mohammad during a TV debate.

BJP spokeswoman Nupur Sharma's remarks sparked uproar among Muslims in India and triggered diplomatic protests from Islamic countries demanding an apology from the Indian government.

Sharma has been suspended from the party while another spokesman, Naveen Kumar Jindal, was expelled over comments he made about Islam on social media.

Police in northern India arrested a BJP youth leader for posting anti-Muslim comments on social media, along with 50 other people who took part insporadic unrest among minority Muslims in parts of India last week over Sharma's remarks.

India's foreign ministry said on Monday the offensive tweets and comments did not in any way reflect the government's views.

Instructions have been issued to several senior members of the BJP to be "extremely cautious" when talking about religion on public platforms. 

But domestic outrage gained fresh momentum after leaders from Islamic nations including Qatar, Saudi Arabia, the United Arab Emirates, Oman, Indonesia, Malaysia, Pakistan, Iran and Afghanistan demanded apologies from New Delhi and summoned diplomats to protest against the remarks in the TV debate.

The influential 57-member Organisation of Islamic Cooperation (OIC) said in a statement that the insults came in the context of an increasingly intense atmosphere of hatred toward Islam in India and systematic harassment of Muslims.

The controversy has become a diplomatic challenge for Modi who in recent years has cemented strong ties with energy-rich Islamic nations.

Reuters