US prosecutors have charged an American citizen with helping to plan the 2008 attack in Mumbai, which resulted in the deaths of 166 people.
David Headley, the first US citizen charged in the plot, was accused on Monday of receiving training from the armed Pakistani group Lashkar-e-Taiba, itself accused of carrying out the lethal attack in Mumbai.
Prosecutors say Headley travelled to the Indian city several times, beginning in 2006, and took pictures and video of some places hit in the attacks.
He had already been arrested in October on charges of plotting to attack a Danish newspaper and its employees over the publication of cartoons of the Prophet Muhammad.
After his trips to India, Headley travelled to Pakistan to turn over the results of his surveillance and, in early 2008, he took boat trips into the Mumbai harbour, according to court documents released by the US justice department.
In November 2008, 10 attackers launched their assault on various targets in Mumbai, including several where Headley had conducted surveillance, according to the documents. The attackers had arrived in Mumbai by boat.
"This investigation remains active and ongoing," said Patrick Fitzgerald, the US attorney for the Northern District of Illinois, where the charges were filed.
"The team of prosecutors and agents will continue to seek charges against the other persons responsible for these attacks."
The charges against Headley include aiding and abetting the murder of six Americans who died in the Mumbai attacks.
A lawyer for Headley declined to comment.