At least 81 people were killed in the western Indian state of Gujarat on Sunday when a footbridge packed with sightseers enjoying holiday festivities collapsed and plunged them into the river below.

Television footage showed dozens of people clinging onto the cables and twisted remains of the bridge over the Machhu River in the town of Morbi as emergency teams struggled to rescue them.

Some clambered up the broken structure to try to make their way to the river banks, while others swam to safety. A number of children were among the victims.

Prateek Vasava, who swam to the river bank after falling from the bridge, told 24 Hours Gujarati-language news channel that he witnessed several children drop into the river.

"I wanted to pull some of them along with me but they had drowned or got swept away," he said.

The bridge had collapsed in just a few seconds, he said.

Atul Prajapati, a medical officer at the state hospital near the disaster site, said: "We have found 81 bodies and the final rites process has begun."

Dozens of people were also injured, officials said.

Authorities said more than 400 people were on and around the colonial-era suspension bridge at the time of the collapse. State Home Minister Harsh Sanghavi said more than 150 people were on the bridge itself. The bridge had drawn many sightseers celebrating the Diwali, or festival of lights, and Chhath Puja holidays.

"Many children were enjoying holidays for Diwali and they came here as tourists. All of them fell one on top of another. The bridge collapsed due to overloading," said one witness, who gave his name as Sukram

The 230-metre bridge was built during British rule in the 19th century. It had been closed for renovation for six months and was reopened for the public last week.

Prime Minister Narendra Modi, who is in his home state Gujarat for a three-day visit, said he had directed the state chief minister to mobilise teams urgently for the rescue operation. (Reuters)