Eleven Indian women have died after undergoing botched sterilisation surgery at a government-run health camp in the central state of Chhattisgarh.

More than 50 others are in hospital - at least 20 are in a critical condition following the tubectomy operations.

Officials deny negligence. Four health officials have been suspended.

State-run sterilisation camps are held to curb India's 1.3bn population. Most of those operated on are women - many poor and often paid to be sterilised.

The tubectomies were carried out on Saturday in Pendari village in Bilaspur district.

Villagers say 83 women - all between the ages of 26 and 40 - were operated on in just six hours by one doctor and his assistant.

Reports say the women started complaining of pain and fever, soon after being operated on. A relative described the conditions at the clinic as appalling.

"They just operated on them and left them. It's a desolate place, there are no facilities there," DR Shinde told the Associated Press.

Preliminary examinations showed the deaths had been caused by infection or shock as a result of blood loss, state deputy health director Amar Singh told the Press Trust of India news agency.

But Bilaspur district health officer Dr RK Bhange told BBC Hindi: "The cause of the death would be known only after the post-mortem report is available."

Correspondents say all the women came from very poor families. Those who survived are receiving treatment in three different hospitals in the district.

"Their condition is very serious. Blood pressure is low, so keeping the circumstances in mind, we are now concentrating on treating them, not on what caused this," Dr Ramesh Murty told reporters.