At least seven Amarnath yatris were killed and 12 others injured when suspected militants attacked their vehicle at Botengoo area in south Kashmir's Anantnag district on Monday evening.
Jitendra Singh, Minister of State in the Prime Minister's Office, called the incidents "most condemnable".
Reports from the area said the firing took place near Khanabal chowk (which is almost a kilometre away from Batengoo) and the firing was still on. He blamed Monday's attack on Muslim militants who are fighting against Indian rule in Kashmir.
Congress vice president Rahul Gandhi also condemned the attack saying that India will never be intimidated by terrorist cowards. "Troops of 90 Bn & 40 battalion of the CRPF were rushed to the spot", said a senior CRPF official, according to news agency, PTI.
The former Chief Minister of Jammu and Kashmir Omar Abdullah condemned the attack and said despite recent successes against militants the feared attack took place. "The attack deserves strongest condemnation from everyone", Modi tweeted. The bus was not registered with Shri Amarnath Shrine Board (SASB) that manages and regulates the sensitive annual pilgrimage.
The mini-bus was proceeding from Jammu to Srinagar.
The police had asked all vehicles carrying pilgrims to cross the Jawahar Tunnel in daylight and avoid travelling in the Valley after sundown.
Soon after the attack, the Internet services in Kashmir were blocked on cell phones and broadband lines.
Prime Minister Narendra Modi put out a series of tweets condemning the "dastardly" attack.
He said he spoke to Governor NN Vohra and Chief Minister Mehbooba Mufti and assured all possible assistance.
The cowardly attack was widely condemned on social media with journalists and politicians cutting across party lines expressing their disgust on the killings of Amarnath pilgrims. State minister Naeem Akhtar said, " First time pilgrims have been targeted and this is a dark chapter in Kashmir's history".
He added further that a CRPF camp located 3.5 km away from the attack site had also been attacked but that jawans had foiled the attack and that nobody had been injured.
The force personnel launched a combing operation to track down the militants responsible for the attack.
"Very sad news. The attack can not be condemned strongly enough".