India’s Prime Minister has said the collapse of a flyover in Kolkata, that killed more than 20 people, was a “message from God” telling the people of West Bengal they must be saved from the state's ruling party.

Speaking at an election rally in Madarit, north Bengal, Prime Minister Narendra Modi said the tragedy illuminated the dangers of the All India Trinamool Congress led by Chief Minister of West Bengal Mamata Banerjee.

“They are saying it is an act of god, but actually it is an act of fraud," said Mr Modi. "It is an act of god in the sense that it happened during election time so that people may know what kind of government she [Ms Banerjee] has been running," The Times of India reports.

“God has sent a message to the people - that today this bridge has collapsed, tomorrow she will finish off entire Bengal. God's message to you all is to save Bengal.”

At least 21 people were killed and more than 150 injured after a partially completed concrete and steel bridge fell on to traffic on a busy road in Kolkata.

Pictures of incident show cars, trucks and rickshaws under huge quantities of debris, while fire fighters and residents attempt to rescue those trapped with their bare hands.

In pictures: Kolkata bridge collapse Show all 15 1 /15 In pictures: Kolkata bridge collapse In pictures: Kolkata bridge collapse Rescue workers cut through parts of a partially collapsed bridge In pictures: Kolkata bridge collapse Firefighters and rescue workers search for victims at the site of an under-construction flyover after it collapsed in Kolkata In pictures: Kolkata bridge collapse A man is seen trapped amid the debris of an under-construction flyover after it collapsed In pictures: Kolkata bridge collapse Locals and rescue workers clear the rubble of a collapsed overpass In pictures: Kolkata bridge collapse Locals and rescue workers clear the rubble of a collapsed bridge In pictures: Kolkata bridge collapse Rescue workers work at the site of a partially collapsed overpass in Kolkata In pictures: Kolkata bridge collapse An Indian soldier looks for survivors under a collapsed overpass in Kolkata In pictures: Kolkata bridge collapse Rescue workers take an injured man for medical treatment after retrieving him from underneath a collapsed overpass in Kolkata In pictures: Kolkata bridge collapse Rescue workers clear the rubbles of a collapsed bridge In pictures: Kolkata bridge collapse Rescue members rush a policeman to an ambulance after he was rescued at the site of an under-construction flyover that collapsed in Kolkata In pictures: Kolkata bridge collapse Indian rescue workers and volunteers try to free people trapped under the wreckage of a collapsed fly-over bridge near smashed cars in Kolkata Getty Images In pictures: Kolkata bridge collapse A long section of a road overpass under construction collapsed in a crowded Kolkata neighborhood, with tons of concrete and steel slamming into midday traffic, killing several and injuring many In pictures: Kolkata bridge collapse Rescuers look at the mangled structure of a vehicle under a partially collapsed overpass in Kolkata In pictures: Kolkata bridge collapse Indian rescue workers and volunteers try to free people trapped under the wreckage of a collapsed fly-over bridge AFP or licensors In pictures: Kolkata bridge collapse Firefighters and rescue workers search for victims at the site of an under-construction flyover after it collapsed in Kolkata

Mr Modi accused Ms Banerjee of being “shamelessly” political over the deaths, after she reportedly blamed the Left Front, an alliance of Indian leftist parties who issued the contract for the flyover project, for the accident, NDTV reports.

Mr Modi said rather than blaming the Left Front, Ms Banerjee should have “assisted in rescue work”.

“It’s the chair which is only visible [for Ms Banerjee] and not the dying people,” he added.

Mr Modi has made further jibes towards the Trinamool Congress, telling an audience in Asansol, the party's letters TMC stood for: "T for Terror, M for Maut, C for corruption".

In response, Trinamool Congress lawmaker, Derek O'Brien, criticised the Prime Minister tweeting: “What PM said was unbecoming of his high office”.

In a statement addressing Mr Modi, Mr O'Brien denied his claims and told the Prime Minster: "We expect you now to grow with your job."

The Trinamool party has claimed that although the collapse happened under their government, the contract was awarded by the state's previous Left Front government.

The Left Front have claimed the Trinamool government continued with the same builder for the project despite it being blacklisted by some states, according to NDTV.