MADRID (REUTERS) - Authorities have shut a primary school in the Basque Country region of Spain after several teachers tested positive for Covid-19, the first to be closed entirely in the week classrooms reopened across the country.

Students have begun to return to school after a six-month shutdown, prompting feelings of relief but also concerns about further infection in the country that already has the most cases in Western Europe.

The government has been criticised by teachers unions and parents groups for making health and safety plans at the last minute, but Education Minister Isabel Celaa said the reopening had gone very well, with cases detected in only a few dozen places.

"We have 28,600 schools...and as of yesterday we had incidents in 53," she told state broadcaster TVE. "This means that school management and administrative staff have done a spectacular job."

A handful of individual classes were sent home and small groups of teachers quarantined earlier this week, but the primary school in the Basque town of Zaldibar was closed entirely.

A spokeswoman for the regional government could not confirm how many teachers had tested positive or how long they expected the school to remain closed for. All staff will be tested.

Spain recorded 4,137 new infections in the past 24 hours, taking its total cases to 554,143 but continuing a fall in daily infections from over 10,000 on Sept 4.

Thirteen deaths were reported, taking the overall toll to 29,699.

"In the last few days there seems to be a slowdown and we could even be facing a stabilisation," health emergency chief Fernando Simon told a news conference, adding that the caseload was falling in half of Spain's provinces.