At least five workers have died and up to 50 others are trapped after a six-storey building under construction in northern India collapsed, a government official has said.

District administrator Kaushal Raj Sharma said the army has been asked to help clear the rubble and search for the missing workers.

The building came crashing down in Kanpur, a city in Uttar Pradesh state.

The building belongs to Mehtab Alab, a politician from the regional Samajwadi Party which governs the state.

Building collapses are common in India, where high demand for housing and lax regulations have encouraged some builders to cut corners, use sub-standard materials or add unauthorised extra floors.

In 2013, 74 people were killed when an eight-story building being constructed illegally in Mumbai caved in.