Bangladesh on Sunday blocked ailing key opposition leader and two-time former premier Khaleda Zia from travelling abroad for life-saving medical treatment, an official and supporters said.

Kayser Kamal, legal chief for Zia’s Bangladesh Nationalist Party (BNP), slammed the government’s decision to bar the wheelchair-bound 78-year-old from leaving — due to the terms of her effective house arrest — as an act of “political vengeance”.

Bangladesh is gearing up for general elections due before the end of January, and several Western governments and rights groups have expressed concern over the political climate in a country where the ruling party dominates the legislature and runs it virtually as a rubber stamp.

Zia and her bitter rival, Prime Minister Sheikh Hasina, have dominated the politics of the South Asian nation of 170 million people for over four decades.

In 2008, Zia was sentenced to 17 years in prison for graft, and jailed for two years before being released under house arrest. She has rejected the charges as politically motivated.

Zia has been hospitalised since early August with advanced liver cirrhosis, breathing difficulties and diabetes, and she suffers from a heart condition, rheumatoid arthritis and knee problems, her doctor has said.

Her family last month wrote to the government pleading to let her fly abroad for treatment.

But Minister for Law Anisul Huq told reporters on Sunday they had rejected the plea, saying the executive order for her release from prison barred her from both taking part in politics and going abroad for medical care.

“The application can’t be reconsidered,” he said.

The existing executive order would have to be cancelled before the government could reconsider a new directive allowing her to go abroad, meaning Zia would have to return to prison first and then apply, Huq said.

Kamal, the BNP legal chief, condemned the decision.

“She was granted a conditional release under a provision, and the same provision can be used to allow her to get treatment abroad,” he said.

Tens of thousands of BNP supporters protested last week against the government’s actions towards Zia.

The BNP and its allies have staged a series of protests since last year demanding Hasina step down and allow a caretaker government to oversee the elections.

Yousuf Ali, a supporter of Zia and British-trained barrister who practices in Dhaka and London, said Huq’s order was issued “in support of the political vendetta” of Hasina against Zia, adding that legally she should be allowed to travel for medical care.

“I do not find any legal impediment to send Begum [Khaleda] Zia abroad for her much-needed life-saving treatment,” Ali told AFP.