Bangladesh's imprisoned opposition leader Khaleda Zia was handed another seven years in prison on Monday on corruption charges her supporters say are politically motivated to prevent her running in a general election.

Zia, long time rival of Prime Minister Sheikh Hasina, is already behind bars after being handed a five-year term in February on separate embezzlement charges.

That verdict triggered clashes between police and thousands of loyalists from the main opposition Bangladesh Nationalist Party (BNP), which Zia still leads from prison.

In her latest trial, Judge Mohammad Akhtaruzzman found the 73-year-old guilty of abuse of power and embezzling 31.5 million taka destined for a charitable fund.

The verdict was handed down in a temporary courtroom inside Dhaka Central Jail where Zia — who has been hospitalised for poor health — is the only inmate.

Her lawyers, who were also absent during the verdict, have consistently described the trial as “political vengeance” by Hasina, who has been accused of stifling her opponents.

The opposition vowed nationwide marches on Tuesday to protest against the guilty verdict.

“The people will never accept this judgement,” BNP secretary general Fakhrul Islam Alamgir told reporters.

This fresh conviction is expected to further impede Zia's chances of challenging her erstwhile ally Hasina in an election slated for December.

Zia boycotted the 2014 general election which saw her arch-rival Hasina returned to power.

The BNP had been hoping a higher court would overturn Zia's earlier sentence, setting her free and paving the way for the veteran opposition leader to run against Hasina.

But the latest guilty verdict throws up more hurdles for the opposition, which says 4,000 of its supporters have been arrested since September in a pre-election crackdown.

Family feud

Prosecutor Khurshid A. Khan said the latest charges against Zia occurred in 2005, during her second term as prime minister of the Muslim-majority democracy of 160 million.

“We finally got justice, despite some delay,” he told AFP.

Zia entered politics in the mid-1980s after her husband, a former military dictator, was assassinated in an abortive coup.

She faces dozens of separate charges related to violence and corruption that her lawyers insist are baseless.

Zia says the charges are designed to keep her family out of politics.

In recent months, her health has deteriorated inside the abandoned 19th century jail. A physician said earlier this month that arthritis had rendered Zia's left hand useless. Her lawyers argued that the government was putting her health at risk by refusing her specialised care in prison.

A special courtroom inside the prison was set up to fast track her trial, a move her lawyers described as unconstitutional.

It is not Zia's first time in prison. She and her son Tarique Rahman spent one and a half years behind bars after being held by army-backed government in 2007 awaiting trial for alleged corruption.

Zia's sentencing was yet another blow for her political dynasty with Rahman, her eldest and heir apparent to the opposition movement, jailed for life in absentia this month.

He lives in exile in London.

Rahman was found guilty of playing a key role in a 2004 grenade attack on one of Hasina's political rallies, which injured the then opposition leader and killed at least 20 others.

Nineteen people were sentenced to death over the attack on Hasina, whose father led Bangladesh's push for independence from Pakistan and long feuded with Zia's own father, an opposition hero.

The guilty verdict comes at a time when the independence of Bangladesh's judiciary is under question.

In a recently-published best-selling memoir, a former chief justice alleged he was forced into exile last year after disagreeing with Bangladesh's powerful intelligence services over a case.

Another judge, who also lives in exile in Malaysia, made similar remarks in a television interview, alleging he was threatened to hand down a guilty verdict against Rahman.