Patna, Jul 3 (IANS): Ten days after an engineering student was abducted for ransom from the Bihar capital, police have failed to make any breakthrough for his safe recovery.

Ravi Kumar, 22, a third-year civil engineering student at the National Institute of Technology in Patna, was kidnapped June 23 from near his rented house here, a police official said.

His abductors have demanded a ransom of Rs.20 lakh to release him while search operations have been intensified in the case, police officer Sushil Kumar said here Tuesday.

Ravi's father Ramesh Rajak said he had lodged a complaint but the police are yet to trace his son.

"Abductors called me thrice demanding a ransom of Rs.20 lakh for his safe release," Rajak said. The kidnappers used Ravi's mobile phone to make the calls, police said.

Rajak, principal of a government school in Madhepura district, told IANS here that he was worried for the safety of his son. "Police have done nothing till date. Only assurances will not make a difference," he said.

Search operations have been intensified and a suspect arrested in the case is being interrogated, he added.

The abductors have threatened to kill Ravi if the ransom was not paid soon, Rajak said.