The Maoist problem has taken a turn for the worse in Chhattisgarh over the past year, senior Congress leader and former Union Home Minister P. Chidambaram said here on Thursday, in the wake of recent incidents of violence triggered by the ultra left rebels."Although some progress was made in Chhattisgarh in controlling Maoism or Naxalism, in the last year or so things have deteriorated," Chidambaram told the media here.He said the situation had improved towards the end of the rule of the United Progressive Alliance government at the Centre."We made considerable progress in Chhattisgarh towards the end of the UPA government. The BJP government in the state has also made progress in the first two-three years. I think in the last year, things have taken a turn for the worse.""Either the Chhattisgarh government has lost control over the situation or the Maoists have regrouped," he said.CISF Head Constable D. Mukhopadhyay and four civilians were killed on Thursday when Maoists blew up a mini bus in which they were returning to their camp after buying vegetables and groceries in Dantewada district, police said.The deadly attack took place four days before the first phase of the Assembly polls in Chhattisgarh. It was also the third Maoist attack in 13 days in the state.A Doordarshan cameraman and three police personnel were killed in a Maoist ambush, also in Dantewada, on October 30.On October 27, the Maoists fired on a contingent of Central Reserve Police Force in Bijapur district, killing four troopers.