In a massive crackdown on militant groups, Indian security officials detained 14 people across the country Friday and Saturday. Of these, 13 were later arrested by the National Investigation Agency (NIA) — a federal security organization — on charges of “organizing themselves to commit terrorist acts in different parts of the country.”

According to local media reports, many of those were arrested in raids conducted in six cities — including in Mumbai, Bangalore and Hyderabad — and had ties to the Islamic State group, also known as ISIS. The NIA, however, did not name any organization in its official announcement about the arrests.

“It's too early to say anything,” a senior NIA official, who spoke on condition of anonymity, told International Business Times, when asked about the affiliations of those arrested. “The investigation is still at a very preliminary stage.”

However, according to local reports, which cited officials of the NIA and the Anti-Terrorism Squad (ATS) in the state of Maharashtra, Mudabbir Mushtaq Shaikh — one of those arrested Friday in Mumbai — was a self-styled leader of Janood-ul-Khalifa-e-Hind, a group believed to have ties to ISIS.

Shaikh was believed to have been in regular contact with Shafi Armar, who heads Ansar-ut Tawhid fi Bilad al-Hind — another ISIS-affiliated group.

“These individuals were planning and making efforts to establish a channel of procurement of explosive/weapons, identify locations to organize training camps including training of fire arms, motivate new recruits to target police officers, foreigners in India and to carry out terrorist activities in various parts of India,” the NIA said, in a statement released Friday.

According to sources cited by local newspapers, the Hindu and the Indian Express, the militants had received instructions to carry out “sensational” attacks across the country, including in Goa, a popular tourist destination in western India.

“As they were under surveillance for the past seven-eight months, we came to know of their intention to target Goa a few months ago,” an Indian government official, whose name was not revealed, told the Hindu. “It was decided not to arrest them then as they neither had explosives nor the organizational skill to carry out the attack. Had we arrested them then, the case could have fallen flat in the court of law later on. We decided to wait and watch.”

The arrests come at a time when security across India has been beefed up in preparation for the country’s 67th Republic Day celebrations Tuesday.

Over the weekend, security officials also blocked access to over 90 websites accused of spreading ISIS propaganda.

“There is a systematic propaganda that is being spread and like the way consumers are attracted to the advertisements, people are being lured to follow the fundamentalist agenda,” Maharashtra ATS chief Vivek Phansalkar reportedly said at a press conference Sunday. “Majority of this radicalization is happening online and we have felt an urgent need to initiate counter-measures. ATS will soon be launching its website and an attempt will be made to effectively use the social media to propagate our counter-narrative.”