Thiruvananthapuram, Oct 28 (IANS): President Pranab Mukherjee and Prime Minister Manmohan Singh Monday spoke to Kerala Chief Minister Oommen Chandy, a day after he was attacked and injured by suspected CPI-M activists.

Chandy is admitted to the Medical College Hospital where the two leaders telephoned him, according to an official statement here.

At least 21 people have been taken into custody and cases registered against 1,000 Left supporters for the attack on Chandy's convoy at Kannur Sunday, police sources said.

Chandy suffered injuries on his forehead, chest and leg after suspected Communist Party of India-Marxist supporters stoned his car Sunday evening.

The incident occurred when Chandy was on his way to attend the annual Kerala Police athletics meet at Kannur. He was flown from Kozhikode Sunday night and brought to the hospital here.

Doctors reportedly told Chandy to be in the hospital for another day as the injury on his chest, if not properly treated, could lead to infection.

Communist Party of India-M state secretary Pinarayi Vijayan said Monday that his party was not involved in the attack.

"Today the credibility of Chandy is at its lowest. At such a time, will we give him an opportunity to get sympathy by unleashing such an attack?" he asked.

"We have done nothing and we want the truth to come out," he said.

Information Minister K.C. Joseph called Vijayan's statement a bluff.

"When their former party colleague T.P. Chandrasekheran was murdered last year, Vijayan said the same thing that they had done nothing wrong. At the end, we all know what really happened."

Joseph wondered what would have happened if a stone had hit Chandy's head.

"This is the first instance in our state where a chief minister has been attacked. Our request is that the CPI-M should desist from violence," he added.

Chandy Monday had a stream of visitors including Governor Nikhil Kumar and opposition leader V.S. Achuthanandan. Bharatiya Janata Party leaders met him too.