New Delhi, Sep 3 (IANS) Sonia Gandhi was Friday elected Congress president unopposed for the fourth successive time, becoming the longest serving Congress chief. Thanking party workers for their support, Gandhi termed the job as a 'great responsibility'.

'Congress workers have all elected me unopposed as head of this great, historical organisation. For this, I am grateful to all of you,' said Gandhi at a brief function to mark her election at the AICC headquarters. The large gathering of Congress workers shouted slogans of 'Sonia Gandhi zindabad'.

At the function, which was also attended by Prime Minister Manmohan Singh, she was presented with a certificate to mark her election to the post for the fourth term. Gandhi had first assumed office of party president in 1998.

Her uninterrupted tenure since then makes her the longest serving head of India's oldest political party, which was founded in 1885 and has ruled independent India for all but 13 years.

'I feel that this post of Congress president is a great responsibility towards the nation,' said Gandhi.

She added that the party represented the aspirations of each and every section of Indian society. 'Whether in power or out of it, we should be mindful of this,' said Gandhi.