NEW DELHI (AFP) - Angry protests broke out in India's capital overnight over power blackouts as summer temperatures soar, fuelling concerns of a repeat of an electricity crisis two years ago, the police said on Wednesday.

Residents took to the streets at around midnight on Tuesday in New Delhi's north-east, attacking vehicles as frustration mounts over the power cuts, a senior officer said.

"So far we have arrested three people for damaging a bus and a gypsy (a jeep) while protesting power cuts in Bhajanpura area," commissioner of Delhi police V.V. Chaudhary told AFP.

Power outages mainly in northern India have been triggered by a spike in demand as temperatures soar, leaving a dilapidated electricity infrastructure unable to cope.

Riots erupted over the weekend in the northern state of Uttar Pradesh, with residents storming a substation near the capital Lucknow.

The Delhi government announced emergency power-saving measures on Sunday, including cutting electricity at the city's shopping malls, turning off street lights and ordering government offices to switch off air conditioners at certain times.

Damage to some transmission lines during a recent major thunderstorm in Delhi, home to more than 16 million people, has added to the problems.

A political row has erupted over the cuts, with new national Energy Minister Piyush Goyal blaming the city's previous Congress government for outdated infrastructure, as authorities scramble to address the problems.

New Prime Minister Narendra Modi and his right-wing party swept to power last month on a pledge to reform the economy, including strengthening energy security and boosting development of solar power.

India has long struggled to meet rapidly rising demand in Asia's third-largest economy, with poorly maintained transmission lines and overloaded grids.

A power crisis two years ago blacked out half the country and left more than 600 million people without electricity.

The two days of massive outages were blamed on Indian states taking power beyond their allocated limits and proved embarrassing for a country that sees itself as as industrialised power.

As temperatures exceeded 45 deg C, social workers warned Wednesday of the deadly consequences for homeless people.

"There has been a rise in the number of deaths among Delhi's homeless in this heatwave," said Mr Sunil Kumar Aledia, a convenor of the Centre For Holistic Development, told AFP.