Red lines: Robert '3D' Del Naja's massive attack on the art world

Massive Attack's founding member Robert "3D" Del Naja is working on their fifth studio album – but he's also been busy in his garden shed in Bristol, creating blood-red paintings inspired by war.

The paintings include ghostly, skeletal figures with their organs showing through transparent bodies, faceless figures standing in war zones. A passenger jet reflected in the glass of a skyscraper recalls the attacks of September 11.

The 12 paintings in the War Paint exhibition at the Lazarides gallery in London were part of the artwork for UNKLE's third album, War Stories, released last year by the electro rock collective. Produced by James Lavelle on his new label Surrender All, the album comes with a 50-page booklet containing 3D's paintings and several ethereal photographs taken by long-term UNKLE collaborators such as Warren du Preez and Nick Thornton Jones. These are also in the War Paint exhibition.

This is 3D's second solo show of paintings; the first, in the late 1980s, was at the Black Bull gallery in Fulham, just before Massive Attack released their first trip-hop album Blue Lines in 1991. He'd just begun to experiment with figurative painting. "I have been pretty slack at painting over the years," 3D says. "I get caught up in music."

3D, a former member of the Wild Bunch crew and a graffiti artist in the 1980s, has always fused art and music, taking it on himself to design all Massive Attack's merchandise, including the album sleeves and on-tour laminates.

The first two Massive Attack albums feature many of his paintings, but he stood aside from the artwork in the last two. "I didn't want to superimpose myself on the band. On 100th Window, Mushroom had left the band and Daddy G wasn't involved. It didn't contain any of my artwork so that it wasn't perceived as some mad ego project."

His latest war paintings include No Surrender (black faceless figures waving white flags, against a red sky) and the cover sleeve's Peace At Last – two ghostly figures with glowing halos – which, he says, has "a Mexican Day of the Dead festival feel". The artwork is a perfect fit with the foreboding quality of this antiwar album.

Lavelle always encouraged 3D to paint. The War Stories project got 3D back into the art studio last year, after too long a gap. 3D says: "We share a political stance, and I had an idea of what images to come up with." An active antiwar campaigner, he and Damon Albarn paid for full-page adverts in the NME opposing the Iraq war.

It took 3D two months to paint 25 works for Lavelle, using brushes and sprays. Nine became album artwork. "I can stare at a blank canvas for a month, but when I know what I want to express, I paint really quickly," he says. He describes the paintings as "snapshots of scenes that tell a story; it wasn't a mission to create the ultimate cover image." His paintings became "more political" than he'd intended when they were designated for particular songs on the album.

"When I had got back into painting again, I wished I could have spent a year doing it because I felt a new channel for that creativity – but I can't do that," 3D says. "I'd get up early to paint and then go to the music studio in the afternoon. I can't take my kit to the studio because I make a mess and get covered in paint."

Other paintings include International Jihad, depicting European Christian carol-singers. "It's a take on the idea of crusaders. When people talk of any religious crusading, we think automatically of negative images of Islam, almost forgetting the impact of the medieval Crusades waged by much of Christian Europe," 3D says. Unbelievable Proof – a skeletal head against a red background – is "an essay about confusion". Hold My Hand – a syringe above an outstretched arm – is "about excess, greed and control; the addict in the clutch of the drug rather than needing support from another human being".

"The paintings speak for themselves, really," 3D says. "It's abstract, but it's also pretty straightforward. I've made it a little obvious in places. I wanted people to catch an idea of what it's about from looking at it quickly, rather than having to study the painting."

As Massive Attack – now featuring Grant Marshall (Daddy G) – prepare to curate the Southbank Centre's Meltdown Festival in June, 3D's painting career will have to go on the back burner for a while.

"I usually paint a few bits and pieces every year, but I haven't really taken it seriously enough to exhibit paintings until now," he says. "I often paint works for people who like my work. I often swap paintings with John Squire [of The Stone Roses]. I wish I could just paint for a while – but I have other responsibilities."

War Paint, to 25 April, Lazarides gallery, London W1 ( www.lazinc.com )