Thousands of teachers lined up for hours in Madrid on Wednesday to be tested for the coronavirus before the start of the new school term next week as concern mounts over a spike in infections.

The regional government of Madrid, which is responsible for education and health care, summoned teachers on Tuesday night to be tested at several schools, prompting accusations of a lack of planning.

At least 5,000 people lined up outside the Virgen de Paloma high school in western Madrid on Wednesday afternoon, according to police at the scene.

Eva Minerva, a primary school teacher who waited for over four hours under a blazing sun to be tested, said the regional government was "exposing all teachers to contamination" because of the difficulty in maintaining social distance while in the queue.

"And then we will be with the children, who can contaminate their families. It's a massacre. I understand that when families see this they tell us 'I'm not taking my child to school'," she added.

Some teachers chanted "Shame!" as they stood in line or called on the head of the regional government of Madrid, Isabel Diaz de Ayuso, to resign.

Teachers unions have called for several days of strikes this month to decry the "improvisation" of measures to contain the spread of Covid-19 in schools.

Carmen, a 58-year-old primary school teacher who declined to give her last name, said she was "outraged" that she was summoned at the last minute to be tested and then had to wait in a long line.

"They treat us like cattle...They make me want to cry," she added.

Spain will require all students aged six or older to wear masks when classes resume next week, and is urging them to wash their hands at least five times a day.

The country was one of the hardest-hit countries when the coronavirus struck Europe this year before a strict lockdown helped reduce the outbreak's spread.

But infections have surged since the lockdown measures were fully removed at the end of June, especially in Madrid, with the rise in infections often linked to the return of nightlife and social gatherings.