New York Governor Andrew Cuomo has compared the state's death toll from the coronavirus to the 9/11 terrorist attacks, as he implored residents to not relax social distancing measures despite the curve flattening.

The 9/11 terrorist attack devastated New York state with 2,753 people losing their lives.

But the novel virus has become a "painful and breathtaking" situation with the number of people who've died in just 39 days since the first case was detected in New York.

"9/11 was supposed to be the darkest day in New York for a generation," Mr Cuomo said during his daily press briefing on Thursday. "We lost 2,753 lives on 9/11. We've lost over 7,000 lives to this crisis. That is so shocking and painful and breathtaking, I don't even have the words for it."

He compared the virus to a "silent explosion" that has overtaken society with its destruction.

"There was no explosion, but it was a silent explosion that just ripples through society with the same randomness, the same evil that we saw on 9/11," he added.

New York state posted its largest rise in its death toll for the third day in a row after 799 people died from Covid-19 on Wednesday. The death toll increased to 7,067.

The state will now bring in more funeral directors to assist in with the number of people who have died.

"If you would've told me as governor I would have to take these actions ... I can't even comprehend where we are at now," Mr Cuomo said.

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But the curve was flattening in the state, and it showed with the lowest number of hospitalisations and people admitted into the ICU on Wednesday since "this nightmare started".

The governor told residents, though, that now was not the time to relax what they were doing.

"Well, we're flattening the curve, that's good news. It is good news. Well, 'now I can relax.' No, you can't relax," he said. "This is all a direct consequence to our actions. If we stop acting the way we're acting, you will see those numbers go up."

Currently about 18,000 people are hospitalised with the virus. On Wednesday, the hospitalisation rate experienced a net increase of only about 200 patients.

"We are saving lives by what people are doing today. Every day that we are New York tough, we are saving life," the governor said.

Mr Cuomo said social distancing was important for the near future to avoid underestimating the virus again.

Hospital bed capacity in New York has increased to handle 90,000 patients after different institutions presented a number of scenarios for how the virus could impact the state.

Even though efforts have been made to increase bed capacity, the state would be unable to handle the worst case scenario, or even the moderate scenario of the virus, so officials were focused on keeping social distancing rules in place to help admittance rates stay down.