Carlos Latuff: The voice of Tripoli – live from Rio

In one cartoon, an Egyptian revolutionary is lying on the ground, blood seeping from his back, into which a dagger bearing the name of Egypt's new military junta has been plunged. In another, drawn only yesterday, Barack Obama stands over Libya, hoisting a flag that's half US and half EU over an oil tower. A third shows a London policeman atop a giant petrol can with the word "Tottenham" emblazoned across it. He is dropping a lit match into it.

These are the work of Carlos Latuff, a Brazilian cartoonist who has become an unlikely star of the Arab spring – and, more recently, cartoonist to protests and conflicts around the world. A smiling, shaven-haired 42-year-old who still lives with his parents in Rio, Latuff has shunned the traditional platform of newspapers and magazines, and turned instead to Twitter – where his pictures, reacting in near real-time to breaking news, are rapidly disseminated among campaigners and held aloft at rallies across the Middle East.

"I'm not producing artworks to illustrate news articles," he says. "My cartoons are directly geared towards activists who can share them and use them for free. They have a message, they support a cause, and they're designed to be spread widely."

It's a far cry from Latuff's humble beginnings as a cartoonist in the early 1990s, working for leftist publications in Brazil. In 1997, a TV documentary about Mexico's Zapatista insurgency prompted Latuff to change tack. "I thought, 'I need a way to support this movement.' So I made two cartoons. I sent them to the Zapatistas by fax, and the response was positive. But afterwards, I realised it would be more efficient and constructive to put the artworks on a website. It would express solidarity with the group and allow them to download the images and use them. That was my first experience with artistic activism through the internet. I began applying those principles to other causes around the world."

Fourteen years on, Latuff now exploits the ever-growing possibilities of the web and social media to the full, responding quickly to Twitter messages from activists worldwide. These might be requests for some artwork supporting their cause, often taking a provocative stance that might be too dangerous for local artists. Sometimes, a tweet alerting Latuff to an issue in North Africa will be converted into a cartoon in Rio, sent out over Twitter and then appear on the streets of Cairo – all in under an hour.

According to Graham Fowell, ex-chairman of the Cartoonists' Club of Great Britain, an increasing number of cartoonists now scour the 24-hour global news, looking for hotspots and then speedily presenting the view from the street – or at least as conveyed through Twitter. "I like Carlos's cartoons," says Fowell. "They're a bit 'colour-Banksy', depicting the ridiculous ironies of our imperfect civilisation, only much quicker. In some ways, they reflect the globalisation of everything – money, commodities, language and perhaps humanity, too – which, in my opinion, is no bad thing."

Not everyone has been so flattering. Since visiting the West Bank in 1999, Latuff has become known for his support of the Palestinian cause; some campaigners claim his work is antisemitic. "Part of the supposed 'evidence' for my antisemitism is the fact that I've used the Star of David, which is a symbol of Judaism," he says wearily. "But check all my artworks – you'll find that the Star of David is never drawn alone. It's always part of the Israeli flag. Yes, it's a religious motif, but in Israel it has been applied to a state symbol; and it's the institutions of the state – the politicians and the army – that I'm targeting. Including the flag of Israel in a cartoon is no more an attack on Judaism than including the flag of Turkey would be an attack on Islam."

Latuff has also turned his attention to police abuse cases in Brazil. "I have been arrested three times in Rio for my cartoons of the police here," he says. Lately, Latuff has focused on political upheaval in the Middle East, particularly in Egypt – a country he has never set foot in. "In January," he says, "some people got in touch and asked me to make some pictures [in solidarity] with protests that were planned in Egypt for 25 January."

Despite the recent revolution in Tunisia, Latuff was sceptical of anything similar happening in the Arab world's most populous country, but he produced five cartoons. One depicted Egypt as the body of Khaled Said, an Alexandrian businessman who was beaten to death by police the previous summer. Said is shouting, "Wake up Egypt", while "#jan25", the Twitter hashtag for the forthcoming protests, is scrawled across his jumper.

The first indication Latuff received of his cartoons' popularity came on 25 January itself – when he saw protesters bearing placards of his work on TV. He quickly set about producing more, responding to the dramatic twists and turns of the 18-day anti-Mubarak uprising, and continuing his efforts even after Mubarak was ousted – turning his ire instead on the generals who replaced him. Those generals have morphed into figures of hate for many Egyptian revolutionaries, who accuse them of stifling the struggle for meaningful change. But, while domestic commentators risk being hauled before military tribunals if they openly criticise the armed forces, Latuff has been free to mock them mercilessly.

Some Egyptians have been irritated by Latuff's ubiquitous presence online, complaining that other cartoonists tackling these issues – including young, local artists like Ahmad Nady and Amr Sleem – are being sidelined. "Latuff's effort and willingness to put his art in the service of revolutionaries is definitely praiseworthy, but I think there might be better ways to do it," says Egyptian lecturer and activist Soha Bayoumi.

"I think the artistic value of his cartoons is not that high; they are too simplistic, literal-minded and quite rudimentary, both in absolute terms and compared to several Egyptian cartoonists currently working on the revolution. His work is overly praised in Egypt, mainly because he's a non-Egyptian who's taking what seems to be a genuine interest in Egyptian politics, and also because he has more freedom to criticise SCAF [the ruling military council] and other political figures, who could harass or sue him if he were a well-known cartoonist in Egypt."

While Latuff has some Lebanese ancestry, he has no other connection to the Middle East. The cartoonist would like to visit Egypt eventually, but believes he would be detained or deported by the authorities. "One day I hope to stand in Tahrir and see it with my own eyes," he says. "That would be a very special moment."