Over 1,000 people gathered in front of Prime Minister Shinzo Abe's office in Tokyo on Monday evening, calling for his resignation and that of his close ally Finance Minister Taro Aso over a suspected cronyism coverup.

Streets were filled with people chanting "No more lies" and "Don't falsify documents" after Aso admitted earlier in the day that his ministry had altered documents over a deal reached in 2016 for the hugely discounted sale of state land to Moritomo Gakuen, a school operator with ties to Abe's wife Akie.

In the documents, references to Akie, whose role in a school project is suspected to have led to the reduced price, were deleted.

"The Cabinet won't resign en masse. We have to make them do so," a protester said.

Some opposition party lawmakers also took part in the rally, with Mizuho Fukushima of the Social Democratic Party saying, "The prime minister's office is shifting blame to the Finance Ministry. Let's put an end to moves that submit politics to private interests."

In the morning, only around 10 people were taking part in the antigovernment rally in front of the prime minister's office, but the number of participants grew gradually from early evening, with some carrying signs reading "Serious national crime" and "All Cabinet members should resign".

The Moritomo Gakuen scandal, which first surfaced in February last year and pushed down Abe's support ratings, has drawn fresh attention since a major Japanese daily reported on March 2 that the ministry documents had been doctored to remove descriptions stating the discounted land sale price was "exceptional."

Abe's wife Akie was initially named honorary principal of an elementary school planned to be built at the site in Osaka but withdrew after the scandal came to light.