“We say no to whites owning our land and they should go,” Mr Mugabe told his supporters at a rally.
The white farmers union said it was regrettable that racial tensions were flaring up again.
The president’s critics say his policy of seizing most of Zimbabwe’s white-owned farms caused the country’s economic collapse from 2000-2009.
Mr Mugabe, 90, has governed Zimbabwe since independence in 1980.
He was re-elected president last year with 61% of the vote, defeating his long-standing rival Morgan Tsvangirai.
The president’s Zanu-PF party also gained a parliamentary majority of more than two-thirds, winning 160 of the 210 seats.
BBC Zimbabwe analyst Stanley Kwenda says Mr Mugabe’s comments are surprising, as the government officially ended its land reform programme about two years ago.
It appears that Mr Mugabe wants to deflect attention from Zimbabwe’s economic crisis, especially worsening unemployment and the closure of firms, our correspondent says.