ISLAMABAD (Reuters) - One of the suspected planners of last month’s attack by gunmen on Mumbai was arrested by Pakistani security forces in a raid on a militant camp, an official with a charity linked to the militant group said on Monday.

The Jamaat-ud-Dawa (JuD) official, who requested anonymity because of the sensitivity of the subject, said Zaki-ur-Rehman Lakhvi was taken into custody following Sunday’s raid on a camp used by Lashkar-e-Taiba fighters outside Muzaffarabad, the capital of Pakistani Kashmir.

“Yes, Lakhvi is among four or five people arrested in a raid yesterday,” said the official, whose JuD charity is regarded as front for the feared militant group.

Pakistani intelligence officers said six men have been arrested, but gave no names, and there has been no official confirmation of the raid.

Lakhvi, one of Lashkar’s operations chiefs, was named as a ringleader in the Mumbai plot by the lone surviving gunman captured in India, according to Indian officials.

He and Yusuf Muzammil, the head of Lashkar’s anti-India operations, gave orders by telephone to the 10 militants who killed at least 171 people in the attack on Mumbai, Indian officials say.

Pakistan has asked for proof that attackers came from Pakistan, while saying it will cooperate with India in the investigation, but tensions between the two nuclear-armed rivals have risen.

The United States has exerted diplomatic pressure on Pakistan to match words with deeds swiftly to stop the crisis worsening, while asking India to exercise restraint.

“I think there’s no doubt that Pakistani territory was used, by probably non-state actors,” U.S. Secretary of State Condoleezza Rice told CNN’s “Late Edition” on Sunday.

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WHAT NEXT?

If Lakhvi’s arrest is officially confirmed, it will raise the question of what the Pakistani authorities will do with him, and whether it will satisfy India.

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President Asif Ali Zardari has said that anyone arrested in Pakistan will be tried there too.

The Pakistani military’s Inter-Services Intelligence (ISI) agency had ties in the past with Lashkar and other jihadi organizations fighting Indian rule in Kashmir, according to analysts, which could reduce the Pakistani authorities’ readiness to be transparent in its handling of the situation.

Laskhar was officially banned by Pakistan in 2001, after it was blamed along with Jaish-e-Mohammad, for a raid on the Indian parliament that almost sparked a fourth war between the two countries.

The militants say Lashkar relocated its base to Indian Kashmir, while its founder Hafiz Saeed quit the organization, but remained head of the charity.

Analysts say there is evidence of Lashkar fighters cooperating with al Qaeda, and fears that these jihadi organizations have become uncontrollable.

The JuD charity, which has thousands of followers, was also designated a militant organization by the United States, but Pakistan has only put it on a watchlist.