In 1977, Ijaz ul Hassan was forced into a blindfold and a noose tightened around his neck inside the infamous prison housed in Lahore Fort, as his torturers pretended he was about to be executed. As a young artist who had done little to hide his contempt for the martial law imposed by General Zia-ul-Haq's repressive regime in the 1970s, his activism had left him in the line of fire. For four weeks, he was held in solitary confinement, routinely placed under a dangling noose and taunted with threats to his family, friends and "collaborators", before his guards reluctantly freed him.
The incarceration was the culmination of decades of political activism that began with Hassan's protests as a student at Cambridge University against the Vietnam War, and continued with his efforts to organise union protests in his home city of Lahore and the poster artwork that he produced to inspire a resistance movement against the military dictatorship in charge of his homeland.
The artwork Hassan made was deemed so explosive that it was censored, refused entry to exhibitions or taken off the walls of museums by gallerists who feared the wrath of the country's brutal regime. Even today, works by Hassan deemed too obscene and seditious for display in the 1970s have still not been shown in Pakistan, although the Canvas Gallery in Karachi recently staged a retrospective of "declassified" works that had previously been hidden from public view.
This week, the Pakistani-born artist is showing some of his images as part of a group exhibition, Figurative Pakistan, opening tomorrow at the Aicon Gallery in central London.
For someone who has always believed in the power of art to affect changes in the real world, today's political climate in Pakistan – where President Pervez Musharraf's declaration of martial law has chilling parallels to ul-Haq's regime three decades ago – leaves Hassan with a bleak sense of repetition. The anger against authoritarianism that he first felt as a young man has in no way diminished.
While he is now one of Pakistan's most revered contemporary artists, Hassan's work is still regarded as subversive, with its graphic images of violence, references to the Vietnam War, and representations of bloody street protests. Until he left Pakistan two days ago, his every step was followed by military guards, while his son, a Harvard-educated lawyer, faces house arrest.
For Hassan, his anger cannot be disentangled from his artistic vision. "I have never been able to distinguish between politics and painting. Politics was unavoidable, right from the beginning. There is always something nasty left behind by the army, when it comes. In the Seventies, I was working with a specialised group of artists and writers to strengthen democracy.
"One of the reasons democracy is so fragile in Pakistan is because we do not build up institutions such as the arts, which are essential for democracy. I wanted to create a culture of resistance. Art and poetry can express a form of not surrendering and present the 'other' view," he says.
The fact that expressing the "other" view endangered his life was a risk Hassan was willing to take then, just as now. "Of course, everybody has a sense of fear at times like these, but sometimes the events and your passions become larger than your fears. My work has reflected what is going on and where my passions lie. When you are involved, you don't stop to reflect on whether your work is dangerous or not. You are too involved," he says.
During the most repressive days of Zia's regime, when every form of dissent was crushed and Hassan's artwork was removed from every gallery in the land, he resorted first to putting his painted messages on posters and political leaflets, and then to using nature imagery and symbols to get his message across. "My paintings were constantly being censored. One time, during the transitional period that led to Zia's rule, I was part of a group show at Lahore Museum that a general, who had been appointed Governor of Punjab, was due to attend. My work was ordered to be taken down. I thought: 'How can it reach people if it's not on show?'
"Since I couldn't get my works out using human symbols, I got them out by drawing on images from nature. A lot of my work was based on phenomena from nature, so my painting called The Wild Berry, for example, shows a tree with new shoots, and where an axe falls on a branch there are several shoots growing out of it. Nature excited me and there was always something political in these works," he says.
Hassan was born in 1940, nearly a decade before India was partitioned to form Pakistan in 1947. Throughout his life, he existed in a political landscape riven by death, torture, and the fight for freedom against authoritarianism. "I was seven when partition happened, so I saw people shooting at each other at railway stations and dead bodies coming in from the other side on trains. Then, later on, there was the war with Bangladesh and the military dictatorships. You had to be a very insensitive rascal not to be influenced by such events," he says.
Now 67, Hassan has not lost his appetite for politics or for art. He has begun sketching works that deal with the nature of Musharraf's reign, in which he intends to reconceptualise Pakistan's flag in camouflage tones and a bouquet of flowers entangled with barbed wire.
"It's absolutely frightening, what's happening," he says. "We have army courts in place, there is no habeas corpus, there is no bail before arrest. The paintings I'm working on will reflect what's happening and my experience of events, which has brought out the same kind of anger I had as a young man, but disenchantment also.
"There are lots of recently witnessed images in my head, images of women protestors being dragged by their hair over the footpaths. I've learnt from the past, the army always leaves something nasty behind and my art reflects that."
Figurative Pakistan, Aicon Gallery, London W1 (020-7734 7575), Wednesday to 8 December