LAHORE, Pakistan — An antiterrorism court in Pakistan on Wednesday convicted Hafiz Muhammad Saeed, the founder of the group that carried out a deadly attack in Mumbai in 2008, on terrorism-related charges and sentenced him to five and a half years in prison.

India and the United States call Mr. Saeed the mastermind of the Mumbai attack, which killed more than 160 people, including six Americans. For years, Pakistan had been under intense international pressure to take action against him and the radical Islamist group he founded, Lashkar-e-Taiba, and the United States has offered a $10 million bounty for him.

“The Hafiz Saeed conviction should have happened many years ago,” said Mosharraf Zaidi, a political analyst based in Islamabad, Pakistan. “That it did not is a measure of the internal tensions, institutional weaknesses and cognitive contradictions within Pakistan.”

In the antiterrorism court in Lahore, the eastern Pakistani city where he was based, Mr. Saeed was found guilty of having links with terrorist groups, raising funds for terrorism and having illegal property, said his lawyer, Imran Gill.