Pakistani security forces have arrested a suspected planner of last month's militant attack on India's finacial capital in Mumbai in a raid on a militant camp in Pakistani Kashmir, sources said on Monday. The Pakistani government has not revealed any details of Sunday's raid at the camp used by Lashkar-e-Taiba fighters in the hills outside the regional capital Muzaffarabad. But the military confirmed a crackdown had started on banned jihadi groups like Lashkar. India and the United States have pressed Pakistan to act against militants suspected of being behind the Mumbai attack in which at least 171 people were killed. There were fears that tensions between nuclear-armed India and Pakistan could rise unless Pakistan cooperated and a four-year-old peace process is already in jeopardy. Intelligence officials, workers with a charity linked to Lashkar and people living nearby say 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 an official from the Jamaat-ud-Dawa charity, widely regarded as a front for the militant group. Pakistani intelligence officers said at least six men were arrested. The military confirmed arrests had been made. “This is an intelligence-led operation against banned militant outfits and organisations,” the military said in a statement. “There have been arrests and investigations are on”. A Lashkar spokesman confirmed that the group was targeted. “Pakistani forces have attacked our camps in Muzaraffabad under pressure from the US and India,” Abdullah Ghaznavi, a spokesman for Lashkar, told Reuters by telphone. He denied the group was involved in the Mumbai attack. 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 had identified the nine dead gunmen, and the places they came from in Pakistan. Rakesh Maria, lead investigator for Mumbai police, said three suspects including one in custody were from Okara district, three from Multan, two from Faisalbad and one from Sialkot. He identified the leader as Ismail Khan, from Dera Ismail Khan. They were also questioning a man arrested in northern India last February, and investigating if there were any links to homegrown militant groups. The man being questioned is an Indian citizen who was caught with maps that highlighted several targets hit in Mumbai.