WASHINGTON • Democratic presidential candidate Joe Biden and the Democratic National Committee jointly raised US$80.8 million (S$112.3 million) last month, the Biden campaign said, the largest amount collected in any month.

Mr Biden, who raised significantly more than April's US$60.5 million, has built a lead over Republican President Donald Trump in national opinion polls, amid the twin crises of the coronavirus pandemic and civil unrest over police brutality in many US cities.

The campaign said on Monday that it had tripled its online donors since February and recorded an average online donation of US$30 last month.

But Mr Trump still holds a massive cash advantage, after three years of fundraising efforts.

Still, the haul demonstrates the progress Mr Biden's fundraising operation has made since the former vice-president secured enough delegates to clinch the Democratic nomination, following a primary contest in which he was often outraised by rivals.

On Monday night, one of those former rivals, Senator Elizabeth Warren, helped Mr Biden raise US$6 million from 620 donors for an online fundraiser featuring both politicians - the most for any Biden event so far.

Several top fundraisers for Mr Biden told Reuters this month they were seeing a swell of support as the country was gripped by widespread protests over the killing of Mr George Floyd, a black man who died in police custody.

The Trump campaign has not announced its May figures.

In April, Mr Trump and the Republican National Committee jointly brought in US$61.7 million, barely edging out the Democrats.

The committee and the Trump campaign raised US$14 million on Sunday, Mr Trump's 74th birthday.

Last week, Mr Trump attended his first in-person fundraiser in months, due to the pandemic.

Mr Biden, who has only recently resumed occasional travel, has continued to hold virtual fundraisers.

In a statement, Mr Biden said: "Just a few months ago, people were ready to write this campaign off. Now, we are making huge dents in Donald Trump's war chest."

Next week, Mr Biden is set to get an additional financial boost from former president Barack Obama, who will join him for a virtual grassroots fundraiser on June 23.

REUTERS, NYTIMES