The United States has publicly rebuked Pakistan after it released an Islamist leader accused of organising the 2008 Mumbai attacks.
A Pakistani court released Hafiz Saeed, who heads the banned charity group Jamaat-ud-Dawa (JuD), from house custody on Wednesday.
He was detained in January following US pressure Islamabad to rein in extremists but was released this week because of a lack of evidence and led Friday prayers at a mosque in Lahore.
The US and India considers JuD to be a front for Lashkar-i-Taiba, the militant group blamed for the attacks that left 166 people dead, including six Americans.
The State Department said it was “deeply concerned” at Saeed’s release, saying the group he led was responsible for the deaths hundreds of civilians including American citizens.
“The Pakistani government should make sure that he is arrested and charged for his crimes,” it said in a statement.
Lashkar-i-Taiba and its leaders remain subject to US sanctions and the government has offered a US$10 million reward for information that brings him to justice.
Saeed was declared a global terrorist by the US and the United Nations over his alleged role in the November 2008 attacks.
Ten gunmen attacked a busy train station, a Jewish centre and a luxury hotel in India's financial capital where they remained holed up for several days before being killed by security forces. Saeed has repeatedly denied involvement but had previously been detained twice briefly following the attacks.
The US president Donald Trump in August accused Islamabad of harbouring “agents of chaos” while secretary of state Rex Tillerson said too many extremists were finding sanctuary in Pakistan.
India has also expressed outrage at the release, saying it appeared to be an attempt by its northern neighbour to “mainstream proscribed terrorists”.