The Bangladesh army said on Thursday that it had foiled a plot by more than a dozen "religiously fanatic" Islamist officers to overthrow the elected government of Prime Minister Sheikh Hasina.

"We have unearthed a heinous conspiracy to overthrow the democratic government through the army," army spokesman Brigadier General Masud Razzaq said in a written statement.

"The attempt has been thwarted with the whole-hearted efforts of army soldiers," the statement said, adding that the plot had been fomented by Bangladeshi expatriates in touch with "religiously fanatic army officers".

Giving details about the failed coup, which was unearthed in December, Razzaq said a major who was now on the run circulated emails to different serving officers detailing a plan to overthrow the government on January 9-10.

The outlawed Islamist group Hizbut Tahrir, banned in Bangladesh in 2009 after it was linked to a car bomb on a politician, was accused of helping to circulate the messages.

Razzaq told local media that the plot involved up to 16 Islamist officers, both active and retired, raising fears about the prevalence of hardliners in the upper ranks of the 140,000-strong military.

Hasina's government, which came to power in early 2009, made changes in June last year to bolster the secular character of the Bangladesh constitution, although Islam was retained as the state religion.

The move sparked a series of angry protests by Islamic activists in Muslim-majority Bangladesh, one of the world's poorest countries and which has a long history of coups and counter-coups.

Two retired officers including a colonel have been arrested and will be presented before a court of inquiry, while an alleged "co-planner" called Major Syed Ziaul Haq, a serving officer, had fled.

A major general who heads one of the largest cantonments in the eastern city of Comilla has been "recalled to the logistics area in Dhaka Cantonment", another spokesman, Shahinul Islam, told AFP, without elaborating.

Syed Ashraful Islam, spokesman of the ruling Awami League party and an influential minister, said: "There is no room for conspiracy in the army. Those who are involved in such conspiracy will be given exemplary punishment."

There were rumours online late last month about a foiled coup attempt after the main opposition leader Khaleda Zia accused the government of "incidences of disappearances" in the army.

The army hit back, terming the allegations "provocative and misleading".

Dhaka University professor Imtiaz Ahmed, a security expert, told AFP that "we've been hearing the rumour of a possible coup for the last couple of weeks. It appears that they handled the situation quite well."

He said it was important the armed forces "seriously dig into the matter as to how much the Islamists were involved, in which capacity and how big was the penetration."

Bangladesh has a history of bloodshed and political violence since gaining independence in 1971.

The country's first president was assassinated during his overthrow by the army in 1975 and Bangladesh was run by a military dictator again from 1982 to 1990.

Democracy was restored in 1991, but street battles between Zia and Hasina's supporters prompted the army to step in again in January 2007.

The government of Hasina, who came to power in 2009, was hit by a military rebellion later that year when 57 army officers were killed by renegade border guards.