Two more members of US President Donald Trump's campaign staff who helped organise his weekend election rally in Tulsa, Oklahoma, have tested positive for coronavirus, the campaign said Monday.

The two staffers, members of the advance team, attended the rally but "were wearing masks during the entire event," said campaign communications director Tim Murtaugh.

"Upon the positive tests, the campaign immediately activated established quarantine and contact tracing protocols," Murtaugh said.

Several hours before Saturday's rally, the campaign said that six members of the advance team in Tulsa had tested positive for Covid-19.

Trump, who is facing a tough re-election battle in November, went ahead with the rally, his first since the pandemic began, despite concerns among health authorities that it could further spread the highly-contagious virus.