One of India's wealthiest temples has apologised after six people were killed and dozens more injured in a crush as they queued for tickets to a festival which attracts hundreds of thousands each year.

The incident took place on Wednesday night after thousands gathered in the temple town of Tirupati in southern Andhra Pradesh state.

Visuals showed a swell of people jostling while the tickets were being distributed at counters set up by temple authorities.

Officials in the state have said strict action will be taken against temple employees who are found responsible for the tragedy.

BR Naidu, chairman of the temple's trust, said that the crush was caused by "overcrowding".

"It is an unfortunate incident," he told local media on Wednesday.

Bhanu Prakash Reddy, a board member of the trust, apologised for the incident.

"To distribute tokens, we opened 91 counters... it is unfortunate that the stampede happened," he said. "This has never happened in the history of the temple. I sincerely seek an apology from the devotees."

Andhra Pradesh Chief Minister N Chandrababu Naidu has expressed his sorrow over the incident - he is due to visit the site later on Thursday.

Prime Minister Narendra Modi said he was "pained" by the incident and assured those affected that the state government would offer them "all possible assistance".

The Tirupati temple in Andhra Pradesh is one of Hinduism's most sacred shrines. Dedicated to Hindu god Sri Venkateswara - popularly known as Balaji – the temple owns assets worth tens of billions of dollars and is one of the richest in India.

It attracts nearly 24 million devotees from India and abroad every year.

Its 10-day Vaikuntha Dwara Darshan is considered a highly auspicious event by devotees as they believe they can get a glimpse of the divine gates of heaven.

Hundreds of thousands attend the festival every year, with the temple saying it was prepared to receive 700,000 people this time.

On Wednesday, thousands gathered to receive tickets for the festival - which begins on 10 January - at more than 90 counters set up by the temple.

As the gates for the counters opened, people rushed towards the counters, leading to chaos, an eyewitness told the Times of India newspaper, adding that there were just four police personnel there.

Several reports say the police had a difficult time managing the crowd.

Authorities say those injured in the crush were rushed to a government-run hospital for treatment.

Accidents are routinely reported at religious events in India, as huge crowds gather in tight spaces with little adherence to safety measures.

Last year, more than 120 people were crushed to death at a religious event in the northern state of Uttar Pradesh.