A top Catholic Church leader in India has joined a call for justice for an elderly nun raped during a robbery at a convent in West Bengal last week and said the country should be as concerned about the welfare of its people as it is about its cows..

Five days after the violent incident, police have invited several people for questioning but no formal arrests or identification of the suspects have been made despite some of them being caught on security cameras.

The pace of the investigation into the March 13 crime, which stoked public outrage, has been painstakingly slow, said Cardinal Baselios Cleemis, president of the Catholic Bishops' Conference of India.

"The country has a responsibility towards all of us — every human being - and not just cows," Cleemis told journalists, Reuters news agency reported.

Cows are considered sacred by many Indians and campaigns to protect cattle are often used to vilify religious minorities

"I would like to request the authorities to ensure justice is done," Cleemis said in Ranaghat town after he visited the nun at the hospital and the convent, ucanews.com reported.

"The sisters have forgiven but justice (should) be made visible and such acts should not happen again."

"I understand that the process has begun... but I'd like to request the chief minister [Mamata Banerjee] to adopt a faster approach and ensure justice is meted out at the earliest," he said, adding that the nun is making a recovery.

At least eight robbers broke into the convent and ransacked the premises. The nun, in her 70s, tried to stop the break-in, but the robbers assaulted her.

Investigators maintained that only one person sexually abused the nun, who required surgery after the attack. Doctors said she would be released in the hospital in the later days to recover.

Protesters have expressed exasperation at the speed of the investigation by taking to the streets, as different mass actions have been taking place in West Bengal and in the national capital Delhi in the past few days.

Hundreds of protesters confronted chief minister Banerjee on March 16 when she visited the nun at the hospital.