At least 27 people were killed and 32 were wounded, including top regional officials of the governing Congress Party, in an attack carried out by Indian Maoist rebels that party leaders on Sunday called an attack on democracy.

The attack was staged Saturday against a political convoy that was returning from a rally in the city of Jadgalapur, in the central state of Chhattisgarh with the rebels detonating a mine planted in the road and between 150 and 250 Maoist gunmen then opening fire on the vehicles, the local PTI news agency reported.

Killed in the events surrounding the attack were the head of the Congress Party in Chhattisgarh, Nand Kumar Patel, and his son, both of whom had been kidnapped on Saturday. Their bodies were found Sunday morning in the Bastar district, the stronghold of the Maoist group.

Party leader Sonia Gandhi and Indian Prime Minister Manmohan Singh, who belongs to the party, on Sunday traveled to the area to visit the wounded, and Singh said on Twitter that the attack was "a black day for democracy."

The Indian National Congress party, usually referred to simply as the Congress Party, is the largest and one of the oldest democratically-operating political parties in the world, has a modern liberal platform considered to be center-left wing in India's political system and is the largest party in the governing coalition.

The Indian government has declared the Maoist rebels - active in more than one-third of India's districts - to be the country's main threat to internal security, and in recent years the violence attributed to the group has caused the most deaths of any conflict in the South Asian giant.

The worst Maoist attack killed about 70 members of the security forces in 2010, the year in which the armed struggle between that group and the state took the lives of an estimated 1,180 people. So far this year, 173 people have died in the conflict. EFE