TOKYO (REUTERS) - Japanese Prime Minister Shinzo Abe on Monday said he received donations from firms that got government subsidies, the first time he himself has faced questions about potentially improper donations, after having lost three cabinet members to scandals.

Abe returned for a rare second term in 2012, pledging to reboot Japan's economy, and his ruling coalition cruised to another big election win in December. His support remains above 50 per cent, high for a Japanese premier.

Abe's farm minister quit last week after questions about his funds threatened to snarl parliament, which has delayed passage of the budget for the year from April.

Last year, two cabinet ministers quit, one for possible misuse of political funds and one for a campaign law violation.

Political analysts have said Abe's government would inevitably be hit hard if more ministers stepped down, but fallout looks limited for now.

Kyodo news agency and the Sankei newspaper said a branch of Abe's Liberal Democratic Party (LDP) in his home constituency got a total of 620,000 yen (S$7,055) from chemical companies that received government subsidies in 2012 and 2013.

Donations by firms within a year of awards of government subsidies are illegal, but Internal Affairs Minister Sanae Takaichi told a parliamentary panel there was no legal problem if the politician was unaware of the subsidies at the time.

"I really didn't know what I didn't know and I can't say more than that," Abe told a parliamentary panel. "It is a problem if politicians exercise their political power to respond to a request in exchange for money," Abe said, adding that discussions by political parties were needed to dispel public concerns.

Economy Minister Akira Amari told reporters he would return 120,000 yen he received in 2013 and 2014 from a company that obtained government subsidies.

"There are thousands of subsidy programmes. It is hard to keep track of them all," he said.

Agriculture Minister Yoshimasa Hayashi said he had received donations from two firms that got subsidies but was unaware of the subsidies at the time.

Hayashi's predecessor quit last week amid questions over his political fundraising, while the education, environment and justice ministers have also denied wrongdoing.

Abe was unlikely to suffer much from the fuss, one political analyst said.

"If this is the scope, I don't think there will be much impact," said independent analyst Atsuo Ito.