By Simon Cameron-Moore
ISLAMABAD (Reuters) - One of the suspected planners of last month's attack by gunmen in Mumbai was arrested by Pakistani security forces in a raid on a militant camp near Muzaffarabad, sources in the capital of Pakistani Kashmir said on Monday.
The Pakistani government has so far been silent over Sunday's raid at the camp used by Lashkar-e-Taiba fighters in the hills outside Muzaffarabad.
India and the United States have pressed Pakistan to act against militants suspected of being behind the attacks, which killed at least 171 people, or risk an escalation in tensions between the nuclear-armed neighbours.
Intelligence officials, workers with a charity linked to Lashkar and people living nearby say the area around the camp was sealed off before security forces moved in to make arrests.
An official with the Jamaat-ud-Dawa charity said Zaki-ur-Rehman Lakhvi, a Lashkar operations chief named by India as a suspect, was taken into custody.
"Yes, Lakhvi is among four or five people arrested in a raid yesterday," said the official, whose JuD charity is regarded as a front for the feared militant group.
A former militant who now has close ties to the JuD also said Lakhvi had been arrested, as did one intelligence official.
All of them were speaking on condition of anonymity because of the sensitivity of talking about security matters.
Other Pakistani intelligence officers said six men were arrested, but gave no names.
Britain's The Times newspaper and The New York Post also said in reports on their websites Lakhvi had been caught.
The surviving gunman captured in Mumbai named Lakhvi and another Lashkar commander, Yusuf Muzammil, as ringleaders in the plot, according to Indian officials.
Indian police said they were also questioning a man arrested in northern India last February and investigating if there were any links to homegrown Islamist militant groups.
The man being questioned is an Indian citizen who was caught carrying maps of Mumbai that highlighted several of the targets that were hit.
Pakistan has asked for proof that attackers came from its soil. It says it will cooperate with India in the investigation but tensions between the uneasy neighbours have risen.
For the past two days they have been arguing over the origin of a hoax call to Pakistani President Asif Ali Zardari on November 28 by someone pretending to be the Indian foreign minister.
The aggressive tone taken by the caller resulted in Pakistani forces going on high alert for almost 24 hours.
The Pakistan government issued a statement after a special meeting of the cabinet's defence committee saying it was "imperative to proactively defuse the prevailing tensions."
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.
The United States fears a confrontation with India could deflect Pakistan from the war on terrorism.
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.
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 organisations 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 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 JuD, however, was just put on a watchlist, although the United States has branded the charity, which has thousands of followers, a terrorist organisation.
ELECTION FACTOR OVERPLAYED
The Indian government's measured response so far contrasts with the tough action its public has called for. The government, which faces a general election in 2009, has been criticised for security lapses in the wake of the attacks on Mumbai.
Yet Prime Minister Manmohan Singh's Congress party, despite general distress over rising inflation, appeared set to fare far better than expected in elections underway in five states.
Results were due late on Monday and the outcome could change, but Congress looked likely to hold onto Delhi and take western Rajasthan state from the Hindu nationalist Bharatiya Janata Party. It was also ahead in the northeastern state of Mizoram.
"The BJP's terror plank hasn't worked. People have started to see through it," said political analyst Amulya Ganguli.
The latest crisis with Pakistan has weighed on investor confidence, already sapped by a slowing economy, but the Mumbai stock market rose on Monday thanks to rate cuts and a stimulus package announced at the weekend.
(Additional reporting by Rina Chandran in MUMBAI; Editing by Paul Tait)