Thiruvananthapuram: Veteran Congress leader and Kerala Assembly Speaker G Karthikeyan, who was undergoing treatment at a private hospital in Bengaluru for liver related ailments, passed away this morning.

The end came at 9.30 AM, his office sources here said.

He was 66 and leaves behind his wife and two sons.

Condoling his death, senior party leader and former Defence Minister A K Antony said Karthikeyan's passing away was a big loss for the party and the state.

"We never imagined even in our dreams that he would leave us so early in life after succumbing to such a serious ailment," he told reporters at Kochi.

Karthikeyan, who was suffering from liver cancer, had been taken to the US for treatment last year after which he was shifted to the hospital in Bengaluru.

Known for his clean image and easy accessibility, Karthikeyan began his political career as an activist of the Kerala Students Union (KSU), the student wing of Congress. He later served as the state president of the Union.

Karthikeyan held the portfolios of Electricity and Food and Civil Supplies in two cabinets of the A K Antony government in 1995 and 2001 respectively. A six-time MLA, he represented Thiruvananthapuram North, Aryanad and Aruvikkara constituencies.

A former AICC member, he also served as General Secretary and Vice President of Kerala Pradesh Congress Committee (KPCC).

Karthikeyan represented Aruvikkara constituency in the present Assembly after winning in 2011 Assembly elections.

Condoling the Speaker's death, KPCC President V M Sudheeran said he had lost one of his long-time friends and it was an 'unbearable loss'.

"Though soft-spoken, Karthikeyan had never hesitated in expressing his views forthrightly when needed," he said.

While Opposition leader V S Achuthanandan described Karthikeyan's early demise as an "irreparable loss" to the entire state, CPI(M) state secretary Kodiyeri Balakrishnan said the leader's passing away was a big loss to the Legislative Assembly.

State Ministers K M Mani, P J Joseph and Adoor Prakash were among those who condoled the death of the Speaker.