Amid growing concern over the safety of the missing 28 policemen in a water reservoir on the Andhra-Orissa border, the government of Andhra Pradesh has pressed two more helicopters from the Oil and Natural Gas Commission to help in the search and rescue operations.

While the deaths of five policemen have already been confirmed, the senior police officials at the spot have expressed fears that the death toll may go up further to at least 12.

Sunday's incident took place when CPI-M rebels attacked the launch carrying policemen from Orissa to Sileru in Andhra Pradesh after an anti-Maoist combing operation in the morning.

Andhra Pradesh Chief Minister Y S Rajasekhara Reddy had a review meeting in Hyderabad with top officials and directed that two more helicopters be pressed into service and all possible efforts be made to rescue the missing policemen.

The chief minister, who will visit the spot of the incident on Monday morning, also discussed the security provided to the leader of the opposition N Chandrababu Naidu [Images], who is presently in north coastal Andhra as part of his Mee Kosam Yatra.

Meanwhile, Director General of Police P Yadav has also reached the scene of the incident in a helicopter and discussed the measures taken to trace the missing policemen including Greyhound commandos.

Varying figures of the policemen travelling in the launch were doing round adding to the confusion. DGP said that 35 policemen were rescued and nine were injured. "Search is on for the others," he said.

The sensational attack has come at a time when the Communist Party of India-Maoist is observing 'Anti Police Week'.

The Special Investigations Bureau, which deals with the gathering of anti-insurgency inputs had warned a fortnight ago that Maoists may carry out a major attack any where in the state. But nobody had thought that the attack will be water-borne because never in the past, they have targeted the police in this way.

The police said five policement were killed, including a sub inspector of police Shankar Rao, two members of the elite Greyhound commando force and two home guards, all from Andhra Pradesh.

Sandeep Shandaliya, deputy inspector general of police, Visakhapatnam [Images] range, said that Maoists fired upon the boat in Machkund reservoir in Malkangiri district of Orissa. "It happened when our force was returning to Sileru," he said.

State Militia Commission, a recently constituted force of the Maoists, attacked the patrolling party of the police near Bodikuttu when they were crossing the Sileru reservoir. The launch was carrying the members of the Andhra Pradesh and Orissa police as well as the personnel of the Greyhounds, an elite anti-Naxal force of Andhra Pradesh.

As the launch sank during the attack, the police personnel had to jump into the reservoir even as the Maoists were firing on them, a police official said. Some policemen also returned fire. As the news of the attack reached Visakhapatnam, two naval helicopter were immediately rushed to save the policemen.

In Hyderabad, state Home Minister K Jana Reddy reviewed the situation with high-level police officials and directed them to take all the possible measures to find and rescue the missing policemen.

CPI-Maoist had constituted the State Militia Commission only 10 days ago to carry out a major attack against the police in Visakhapatnam tribal area, which has seen several encounters and other incidents in the recent months.