Pakistani authorities have freed on bail the alleged mastermind of the deadly attacks that killed 166 people in the Indian city of Mumbai in 2008.
Jail officials in Rawalpindi said Zaki-ur-Rehman Lakhvi was released on April 10.
His lawyer, Malik Nasir Abbas, described Lakhvi's release as a "triumph for law and justice."
India said it was an "insult" to the victims of a series of bomb and gun attacks on India's financial capital, Mumbai, in November 2008.
"The global community should take serious note of Pakistan's double-speak on terrorism," a spokesman for India's Home Ministry said.
India's Ministry for External Affairs said, "The fact is that known terrorists not being effectively prosecuted constitutes a real security threat for India and the world."
The U.S. State Department said on April 10 that it was "gravely" concerned about Lahkvi's release.
U.S. State Department spokesman Jeff Rathke said U.S. officials were considering what steps to take next.
Lakhvi had been in jail since 2009.
His release comes after months of wrangling over his detention when a judge granted him bail in December.
His lawyer said the Lahore High Court ordered his release on April 9, conditional on a $20,000 bond.
Lakhvi, chief of the banned Pakistani militant group Lashkar-e Taiba (LeT), is charged with masterminding the Mumbai attacks.
Ten gunmen infiltrated Mumbai by boat and spent three days spraying bullets and throwing grenades around city landmarks.
The violence was blamed on militants of the LeT.
However, the cases against Lakhvi and six other suspects have made no progress in more than five years.
Pakistan has alleged India failed to provide crucial evidence.
Lakhvi was also granted bail in January in another case pertaining to the 2009 kidnapping of an Afghan citizen.