"My anger is so strong that I can feel the taste of blood in my mouth when I see TV pictures of US marines, Swedish mercenaries or Nato soldiers in Afghanistan, " he told an audience at St Xavier's College in Mumbai, India.
"And my deepest personal feeling then is that the only good foreign soldier on Afghan soil is a dead one."
The comments were made on Saturday, a day before two Swedish soldiers were shot dead by an as yet unidentified attacker when they were patrolling in northern Afghanistan.
"This is a horrifying and shocking statement if it is correct. I don't know what got into him," Allan Widman, defence spokesman for the Liberal Party (Folkpartiet), a member of the government coalition, told The Local.
"It's both cruel and cynical towards Swedish troops in Afghanistan, as well as their families here."
Myrdal, a prominent member of the anti-war pressure group Afghanistansolidaritet, was not available for comment. But the chairman of the group, Stefan Lindgren, said the author has a tough anti-war stance and is "very stubborn about using this formula", referring to Myrdal's comment on soldiers in Afghanistan.
"I would not express myself in those terms. Our soldiers are going over there under false presences, but I sympathize with their families and I'm personally sorry it has not been possible to get them home alive," said Lindgren.
In recent months, the Afghanistan debate in Sweden has mainly centred on providing better support to Swedish troops, particularly in terms of equipment such as helicopters, which have been plagued with delays.
Recent opinion polls indicate that almost a half of Swedes continue to support Swedish military involvement in the Nato-led force, which began in 2002, while just over a third want to see a troop withdrawal.
The Left Party, which is the only political party openly calling for a return of all Swedish troops, has been careful not to attempt to gain political capital from the latest military casualties, but continues to argue that Sweden should limit its involvement in Afghanistan to civilian-led development aid.
"The debate now is too much about supporting our troops in these hard times but this is not the real issue. It is not only about the troops but also about Afghan civilians who are more and more affected by the conflict," said Left Party spokesperson, Rossana Dinamarca.
”The troops are there because the government wants them there, but after eight years of Swedish involvement things have not improved. It's time to change the strategy."