The nuclear-armed South Asian neighbours, who have fought three wars over Kashmir, claim the region in full but administer it in parts.
The killings on 22 April had sent shockwaves through India and the case was handed over to NIA, a federal investigative agency.
Security forces had launched a major search and combing operation in the region and thousands were detained across Kashmir for questioning.
The three attackers are, however, yet to be caught.
In a statement on Sunday, NIA said the arrested men had “knowingly harboured the three armed terrorists at a seasonal dhol (hut)” before the 22 April attack. It did not give details of when the arrests took place and as those arrested are in custody, they have not made any statement.
A little-known group, The Resistance Front (TRF), allied with the Lashkar-e-Taiba, had initially said it was behind the attack but later disowned it.
Within days of the attack, India revoked the 1960 Indus Waters Treaty, a long-standing water-sharing agreement with Pakistan. Islamabad, in turn, withdrew from the 1972 Simla agreement that sought to settle differences through bilateral negotiations and peaceful means.
India followed it by launching air and missile attacks on 7 May, targeting sites it called “terror infrastructure in Pakistan and Pakistan-administered Kashmir”.
Pakistan denied the claim that these were terror camps and also responded by firing missiles and deploying drones into Indian territory.
The hostilities between the two countries continued until 10 May when US President Donald Trump announced a ceasefire.
