NEW DELHI, May 6 (Reuters) - A top scientific adviser to the Indian government warned on Wednesday the country would inevitably face further waves of the coronavirus pandemic, as almost 4,000 people died in the space of a day.

With hospitals scrabbling for beds and oxygen in response to a deadly second surge in infections, the World Health Organization said in a weekly report that India accounted for nearly half the coronavirus cases reported worldwide last week and a quarter of the deaths.

Many people have died in ambulances and car parks waiting for a bed or oxygen, while morgues and crematoriums struggle to deal with a seemingly unstoppable flow of bodies.

The government's principal scientific adviser, K. VijayRaghavan, warned that even after infection rates subside the country should be ready for a third wave.

"Phase 3 is inevitable, given the high levels of circulating virus," he told a news briefing. "But it is not clear on what timescale this phase 3 will occur... We should prepare for new waves."

Prime Minister Narendra Modi's government has been widely criticised for not acting sooner to suppress the second wave, after religious festivals and political rallies drew tens of thousands of people in recent weeks and became "super spreader" events.

"We are running out of air. We are dying," the Booker Prize-winning author Arundhati Roy wrote in an opinion piece that called for Modi to step down.

"This is a crisis of your making," she added in the article published on Tuesday. "You cannot solve it. You can only make it worse....So please go."

India’s delegation to the Group of Seven foreign ministers’ meeting in London is self-isolating after two of its members tested positive for COVID-19, Britain said on Wednesday

Foreign Minister Subrahmanyam Jaishankar, who is in London, said in a Twitter message that he would attend virtually.