Geneva, The World Health Organization (WHO) has urged all countries to unite against the COVID-19 pandemic, warning that "millions could die" without aggressive action.

"Almost half a million people have already been infected, and more than 20,000 have lost their lives. The pandemic is accelerating at an exponential rate," WHO Secretary-General Tedros Adhanom Ghebreyesus warned at the G20 Extraordinary Leaders' Summit on COVID-19 held via a teleconference on Thursday, Xinhua reported.

WHO reports show that the first 100,000 cases took 67 days; the second 100,000 took 11 days; the third 100,000 took four days and the fourth 100,000 just two days.

"Without aggressive action in all countries, millions could die. The full social, economic and political fallout, only time will tell," Tedros said.

He raised three requests to address the global crisis that demands a global response. The first is to fight. "Fight hard. Fight like hell. Fight like your lives depend on it -- because they do. The best and only way to protect life, livelihoods and economies is to stop the virus. No excuses. No regrets," the WHO chief proclaimed.

"We must immediately build, expand, train and deploy health workers to find, test, isolate and treat every case and trace every contact," he added.

The second is to unite. "No country can solve this crisis alone. We're all in this together, and we will only get out of it together," he said, urging global solidarity from all countries.

The third is to ignite. "Repurpose the industrial might of your nations for this effort. Ignite global production for the tools we need to save lives now. Ignite innovation for vaccines and therapeutics. And ignite a global movement to ensure this never happens again," he said.

"The actions we take now will have consequences for decades to come," the WHO chief said, as COVID-19 is also the opportunity for everyone to "come together as one against a common threat, and to build a common future."