NEW DELHI/CALCUTTA, 24 January India charged six people with murder yesterday for an attack on Tuesday in Calcutta outside the American Cultural Center that killed four police officers. The six included three teachers of an Islamic school and three Bangladeshis. In addition, 55 people, mostly Muslims, were detained for questioning in the eastern metropolis, drawing flak from Muslim community leaders who called the exercise a pogrom.

Indian officials backed down from their earlier statements that the attack, which wounded 30 other people, was the work of terrorists, and said it was too early to know.

Asked if terrorists were responsible for the attack, Foreign Ministry spokeswoman Nirupama Rao said yesterday: "This attack, the criminal incident yesterday, is still being investigated. We expect to have a more authoritative version from the evidence available."

The three religious teachers and three Bangladeshis were arrested Tuesday night near the India-Bangladesh border, about 65 lm (40 miles) north of Calcutta, said Sourin Roy, chief secretary of the West Bengal state government. The six have been charged with murder and waging war against the state, and face life imprisonment if convicted, he said.

Some police sources put the number of people picked up for questioning in the "hundreds" and said a majority of them were Muslim residents. Siddikullah Chowdhury, state president of the Jamiatul Ulema-e-Hind, accused West Bengal state’s Marxist administration of using the attack as an excuse to harass local Muslims.

"Terrorism has no caste and so why are the peace-loving Muslims of West Bengal being harassed?" the widely respected leader asked. "It is nothing but an anti-Muslim pogrom and if this continues then the peace of our state and city will be destroyed forever."

Police said they also seized a motorcycle belonging to Korban Ali, one of the arrested teachers, and said it may have been used in the attack.

Police said video footage taken by a closed circuit TV camera at the American center had established there were two attackers riding on one motorcycle. Police had earlier believed there were four men riding two motorbikes.

Roy said investigators were attempting to establish whether the suspects were linked to Pakistan’s spy agency or to an underworld figure living in Dubai. Indian officials said they received telephone calls on Tuesday from a "mafia don" in Dubai and from Harkat-ul-Jehadi Al-Islami, a Pakistan-based group, claiming responsibility for the attack.

Both Pakistan and Harkat denied Tuesday any involvement in the attack. UN Secretary-General Kofi Annan said the attack was "worrying" but he hoped it would not further inflame tensions between India and Pakistan. Annan was speaking during a brief stopover in Bangkok en route to his peacemaking mission to Pakistan.