There have been violent protests against the police in Patna, the capital of the Indian state of Bihar, leaving several people injured.

Disturbances broke out during a demonstration against rising crime and what the protesters describe as police atrocities.

The demonstration follows the recent kidnapping of a doctor that led to a two-day strike by medical staff.

Bihar is widely considered one of the most lawless areas of India.

Fatal shooting

The kidnapping on Wednesday of Dr Bharat Singh, an orthopedic surgeon at the Patna Medical College hospital - sparked a wave of indignation in Bihar's health services.

There was already considerable anger in the state over recent incidents, including the fatal shooting of a lawyer and kidnappings of other medical staff.

Even though he was released late on Friday, opposition parties went ahead with their demonstration on Saturday.

Some of the protest leaders had been detained earlier in the day by the police and put into two government buses.

Demonstrators attacked the buses and set them free, before setting the buses alight, the AFP news agency reports.

There was sporadic fighting elsewhere in the city.

Gagged and blindfolded

Critics of the police say it is clear they could do more to prevent the kidnappings.

"When pressure is applied on the government it reacts. An assurance is given that the person will be freed and he is. What are we to deduce from that?" Sailesh Singh of Patna's District Bar Association told the Indian Express newspaper on Thursday.

After Dr Singh's release on Friday, he told reporters that he and a relative had been gagged after the kidnappers stopped their car.

"The abductors had me and my cousin blindfolded and kept us in a room, but they behaved well and provided us food."

The kidnappers have not been identified.

During the doctors' 48-hour strike, at least 10 patients died from lack of medical care.

'Mistaken identity'

The chief minister of Bihar, Rabri Devi, has asked the country's Central Bureau of Investigation to investigate allegations of police brutality in the state.

Her call follows the reported killing of three youths by police last Saturday.

The chief minister has also asked the bureau to investigate the killing of two people earlier this month in a case of alleged mistaken identity.

There has also been anger over the recent killing of a soldier in an incident with the police.