India’s Prime Minister Narendra Modi summoned New Delhi's police commissioner on Friday after the latest attack on a Christian institution, amid claims his Hindu nationalist government is failing to protect religious minorities.

Modi ordered a police crackdown after a Catholic school was burgled overnight in the Indian capital, forcing its closure for the day, the sixth attack on a Christian building in the city since December.

"Prime Minister Modi called me over the recent cases of vandalism of Delhi churches and strictly instructed (us) to track down the culprits," commissioner B.S Bassi told reporters.

"We have increased security around churches and are taking the case with utter seriousness. He asked us to ensure no such attacks take place in future," he said.

Modi said in a statement he asked the commissioner to "speedily investigate the recent incidents of vandalism" but did not specify those on churches and the school.

Priests, nuns and parishioners clashed with police earlier this month as they staged a protest in Delhi over what they said were five church vandalism and arson attacks since December.

Clergy accused Modi's government of failing to speak out against the attacks which they blamed on Hindu hardliners.

Critics say hardliners have felt emboldened since Modi's Hindu nationalist Bharatiya Janata Party (BJP) stormed to power in general elections last May.

Police said burglars broke six CCTV cameras and stole about 8,000 rupees ($128) from donation boxes at the Holy Child Auxilium School, but said the attack did not appear to be motivated by religion.

Father Dominic Emmanuel, spokesperson of the Delhi Archdiocese, rubbished the comments, saying there was a clear pattern of attacks against Christian institutions.

"Police are trying to take an escape route. No one will break into a school with an intent to steal money, it wasn't a bank," Emmanuel told AFP.

"The police are not taking matters seriously and are downplaying the incidents by terming them petty crimes," he said.

Police denied dragging their feet on the other cases, including one this month in which church ceremonial items were stolen and an arson attack on a church in December.

"We suspect it to be an insider's job as they knew exactly where cash was kept," Bassi said of the school break in, adding, "the cases of vandalism will be solved soon."

Hardliners have been accused in recent months of trying to convince Muslims and Christians to convert to Hinduism, sparking outrage from political opponents in parliament.

While Hindus account for more than 80 percent of India's 1.2 billion population, the country is officially secular and is home to sizeable numbers of Muslims, Buddhists and Christians.