(CNN) A bomb ripped through a packed movie theater in northern India on Sunday, killing at least six people and wounding at least 30 others, authorities said.
Sunday's attack at a movie theater is the second apparent terror attack this week in northern India.
The blast in Ludhiana , an industrial town in India's Punjab state, is the second apparent terror attack this week in northern India. Two people were killed days earlier in the bombing of a venerated Muslim shrine in the neighboring state of Rajasthan.
Sunday's attack occurred on one of the holiest days of the Muslim calendar, Eid al- Fitr , which marks the end of the holy month of Ramadan, and came weeks before two major Hindu festivals, Dussehra and Diwali .
The Shringar cinema was packed when the blast occurred around 8:50 p.m. in one of its three theaters. Some 600 people were taking in a recently released Bollywood romance, " Janan Janam Ke Saath ," or "Together Through Several Lifetimes," the Press Trust of India news agency reported.
India television broadcast scenes of shattered windows and glass doors in the cinema's lobby, and the CNN-IBN television news channel said some of the wounded had lost limbs in the blast.
A senior police official, Ishwar Singh, told reporters that the explosion was caused by a single bomb.
Six men were killed -- two who died in the blast and four who later succumbed to their injuries, he said. At least 30 others were wounded, he said. Other officials warned that the death toll could rise.
Authorities said Thursday's explosion, which took place in the town of Ajmer , was caused by a small bomb packed inside a tin lunch box that was detonated during evening Muslim prayers. Police also discovered another bomb at the shrine that had apparently failed to detonate.
No one has claimed responsibility for either attack. But investigators said they interrogated Indian and Bangladeshi pilgrims in connection with the bombing of the Muslim shrine, although they have so far made no arrests.
Officials offered no evidence of a link between the two attacks.
India has routinely blamed Pakistani and Bangladeshi-based Islamic militants for a series of attacks that have rocked the country over the last two years, saying they were meant to provoke violence between India's Hindu majority and Muslim minority. However, little concrete proof has been provided in the past.
Relations between Hindus, who make up more than 80 percent of India's population, and Muslims, who account for about 130 million of India's 1.1 billion people, have been relatively peaceful since the bloody partition of the subcontinent into India and Muslim Pakistan at independence from Britain in 1947. But there have been sporadic bouts of violence