Bangladesh authorities sacked a senior prosecutor after he condemned court cases against Nobel laureate Muhammad Yunus as "judicial harassment", officials said Friday -- prompting him to reportedly seek asylum at the US embassy with his family.

Yunus, 83, is credited with lifting millions out of poverty but has fallen out with Prime Minister Sheikh Hasina, who has said he is "sucking blood" from the poor.

The 2006 Peace Prize winner's troubles began after he mounted a short-lived effort to found his own political party, presenting a challenge to the ruling elite.

He now faces nearly 200 cases and up to six months in prison over labour disputes related to social business firms he set up in the South Asian nation in an effort to create vital jobs and bring services to the poor.

Last week 160 global figures including former US president Barack Obama and ex-UN secretary-general Ban Ki-moon published a joint letter decrying the "continuous judicial harassment" of the micro-credit pioneer.

The signatories -- including more than 100 of his fellow Nobel laureates -- said they feared for "his safety and freedom".

Subsequently, deputy attorney general Imran Ahmed Bhuiyan refused to sign a statement denouncing the letter.

"It is a judicial harassment," he told reporters.

Law minister Anisul Huq said Friday that Bhuiyan had been dismissed for making the comments without permission from the attorney general's office.

"He lied against the government while being in a government office. For these reasons, he has been dismissed," Huq told reporters.

Hours after his dismissal, Bhuiyan took his wife and three children to the US embassy in Dhaka and sought refugee status, the Daily Star newspaper reported.

He told the paper that he had received threats for four or five days.

"This government repays love with imprisonment," it cited him as saying in a text message.

"I don't have a US visa; I somehow managed to leave home with just three bags and my three daughters, and am sitting here. Pray for us."