Pakistani authorities arrested Hafiz Saeed, the alleged mastermind of a four-day militant attack on the Indian city of Mumbai in 2008, on Wednesday on terrorism financing charges.
U.S. President Donald Trump welcomed the move and said it was the result of pressure from his administration on Pakistan to get tougher on militants, while an Indian government official said that merely arresting Saeed was not enough and that he should be put on trial and convicted.
The arrest, announced by the spokesman for the chief minister of Punjab province, came days before a visit to Washington by Prime Minister Imran Khan, who has promised to crack down on militant groups operating in Pakistan.
Previous U.S. administrations have also urged Islamabad to crack down on militants.
Saeed would often address public rallies and regularly give sermons at Pakistani mosques besides leading a political party his charity group founded.
Saeed, designated a terrorist by the United States and the United Nations, is the founder of Lashkar-e-Taiba (LeT), or Army of the Pure, the militant group blamed by the United States and India for the Mumbai attacks, which killed more than 160 people.
He has denied any involvement and said his network, which includes 300 seminaries and schools, hospitals, a publishing house and ambulance services, has no ties to militant groups.
A spokesman for Punjab Governor Shahbaz Gill said Saeed was arrested near the town of Gujranwala in central Pakistan.
The Punjab Counter Terrorism Department said in a statement that Saeed had been arrested while going to a court in Gujranwala to seek pre-arrest bail but was remanded in custody.