Sonia Gandhi was Friday re-elected unopposed as the Congress president for a fourth successive term, adding to her record as the longest serving chief of the 125-year-old party.

At a function at the All India Congress Committee (AICC) headquarters attended by Prime Minister Manmohan Singh, union ministers, Congress Working Committee members and Congress workers from different parts of the country, Gandhi was handed the certificate of her election as party chief by Oscar Fernandes, chairman of the Congress Election Authority.

Cheered on by party workers, Gandhi in her brief speech said that whatever contribution she had been able to make to the country and society was due to the ethos of the Congress.

'From the beginning, the Congress has been representative of every section, every generation, every part of the country. Whether we are in power or not, we should always be conscious of this. While discharging my duty, whatever contribution I have been able to make towards the country and society, it has been due to this feeling,' she said.

Thanking party workers and leaders for re-electing her, Gandhi said that working as party president she had realised that the position was of enormous responsibility.

Describing the Congress as a great organisation with a proud past, she said all the party workers should strive to keep the party flag flying high.

Earlier, Fernandes declared Gandhi elected unopposed. 'I hereby declare Sonia Gandhi declared elected unopposed,' he said.

Soon after Fernandes made the announcement, Manmohan Singh and AICC treasurer Motilal Vora greeted Gandhi with a bouquet.

The Congress office was in a celebratory mood since Friday morning in anticipation of the formal announcement of Gandhi's re-election. Intermittent showers delayed the function by about 90 minutes but did not dampen the enthusiasm of Congress workers. They raised slogans of 'Sonia Gandhi zindabad,' waved party flags, burst crackers outside the party office and danced to the beat of drums to celebrate the occasion.

While workers from Delhi were present in sizeable numbers, party supporters from other parts of the country also came to the AICC office to be part of the celebratory mood.

'We are elated over her re-election. She listens to party workers and has strengthened the party. The party will make progress under her leadership,' said Ravi Kant Rai, a Congress worker from Ghazipur in Uttar Pradesh.

Gandhi will meet union ministers and senior party functionaries at her official residence Saturday. Workers from Delhi will also meet her.

Gandhi first became the party president in 1998. Sewing up alliances in the 2004 polls to oust the Bharatiya Janata Party-led government at the centre, she also led the party to victory in the 2009 general elections. She declined to be the prime minister after the 2004 polls and took the wind out of the sails of the campaign by some opposition parties about her foreign origin.

She headed the National Advisory Council (NAC) during the first United Progressive Allaince government and made suggestions to the government to improve its social sector legislation including the National Rural Employment Guranatee Act and the Right to Information Act.

The NAC was reconstituted this year with Gandhi as its chairperson. It is now examining the proposed food security bill and a bill on preventing communal violence, among other issues.