KABUL — The novel coronavirus is sweeping through Afghanistan's security forces, according to senior Afghan security officials from four provinces who report suspected infection rates of 60 to 90 percent among their units — reducing the number of forces available to conduct operations or take up duty at outposts.

Few have died, the officials say, but little to no testing capacity has forced many into weeks of isolation, leaving deployable forces stretched thin at a time when the country is under pressure from both increased Taliban violence and from the United States, where officials are eager for the government and militants to begin direct talks.

Afghanistan has extremely low coronavirus testing rates: Less than 0.2 percent of its population — 64,900 people out of an estimated 37.6 million — has been tested. As of Thursday, more than 30,000 people were confirmed to have contracted the coronavirus and more than 670 had died. But the Health Ministry warns that the true numbers are much higher, and that as many as 26 million people in the country could be infected with the virus in coming months and that the death toll could top 100,000.

The Afghan government refuses to release data on the number of coronavirus cases within the security forces. Spokesmen from the Defense and Interior ministries acknowledge that there are cases within the security forces but say the virus’s spread has been contained because troops displaying symptoms are quickly isolated, masks have been made mandatory and medical supplies have been distributed to bases nationwide.

Security officials from Nangahar, Ghazni, Logar and Kunduz provinces — all heavily contested by the Taliban — spoke to The Washington Post about infection rates within their ranks on the condition of anonymity because they were not authorized to talk to the media.

Compounding concerns about an effective security force is the diminished presence of U.S. military support. The United States has withdrawn thousands of troops in recent months as part of a peace deal with the Taliban. And worries early in the pandemic about the vulnerability of Afghanistan’s security forces to the virus caused U.S. troops to halt joint ground operations and restrict movement between Afghan and American bases, according to two Afghan officials who spoke on the condition of anonymity because they were not authorized to talk to the media. U.S. forces also suspended most in-person training, according to a quarterly inspector general report.

Resolute Support spokesman Sonny Leggett said joint counterterrorism operations were not stopped because of coronavirus concerns, pointing to coalition forces responding to a militant attack in Kabul in May as evidence that such operations continue.

In Herat, one of the epicenters of the virus’s outbreak in Afghanistan, Police Chief Obaidullah Noorzai said only 36 positive cases were registered among the thousands of police officers under his command. He also said he has received ample support from Kabul and U.S. forces in Afghanistan to contain the virus.

But other commanders on the ground say those numbers are skewed by extremely limited testing. At some bases, commanders reported receiving no testing kits and no additional medical supplies.

“The Ministry of Defense didn’t give us anything,” said an Afghan military commander stationed in Ghazni province. “No one assisted us; there was no medication; no one gave us even the simplest medicine.” The commander said nearly all the troops under his command showed symptoms of the coronavirus at one point over the past month.

Without any testing kits, he said, he had no choice but to quarantine most of his forces.

Over the past month, Taliban attacks have also ratcheted up as the militants looked to pressure the Afghan government to release more prisoners ahead of expected direct talks between the two sides. The Afghan government, normally reluctant to release security force casualty figures, said that last week was the deadliest for its forces in 19 years, with 550 wounded and 291 killed, according to the National Security Council.

“We’re looking at beleaguered forces under the best of circumstances,” said Michael Kugelman, an Afghanistan researcher at the Wilson Center in Washington. Potential outbreaks of the coronavirus within the ranks of Afghanistan’s security forces could affect war-fighting capacity and morale, but “I think the bigger issue is that it could further embolden the Taliban,” he said.

Taliban fighters are probably also suffering coronavirus infections, Kugelman said, but that won’t stop the group from attempting to use the outbreak to “take advantage tactically, and to strengthen its bargaining position in future talks.”

The virus not only has spread through the Afghan forces’ lower ranks but also has killed senior figures, including the chief of police in Kunduz, a district-level police chief in Balkh province and a mid-level police officer in Kabul.

The Afghan Defense and Interior ministries say they have taken measures to prevent the spread of the virus at bases and outposts, such as closing dining facilities and requiring the wearing of masks. The ministries also said they have begun serving troops food with more vitamins, although this is not a measure generally recommended to combat the coronavirus.

But no lockdown measures have been put in place, and security forces are continuing to take regular leave to visit their families, potentially circulating the virus between the communities they are from and the bases where they serve.

The United Nations estimates that Afghanistan could have one of the highest rates of coronavirus infection in the world. The country extended a nationwide lockdown this month, but the measures have been poorly enforced. In both Herat and the capital, Kabul, the two cities with the highest rates of infection, roads remain congested and markets are full of shoppers.

At one graveyard in western Kabul, the manager has had to double the number of gravediggers over the past month to deal with the spike in deaths. Zia Hassani, 35, has been working at the cemetery for the past two years and said five to eight people normally would be buried a day, but now the number is 20 to 40.

“Only in the days that big suicide attacks happened did people bring this many bodies,” Hassani said, referring to the deadly bombings that for years were a near-weekly occurrence in Kabul.

Hassani and Ali Jafari, 22, who works alongside him, said they aren’t told the cause of death for those they bury. But Hassani said he thinks many have died of the virus.

“The government hides the real numbers because it doesn’t want to panic the public,” he said. “But I know it, I work here, and I see that the deaths are higher.”

Correction: An earlier version of this story mischaracterized the response from Sonny Leggett, a spokesman for the U.S. military command in Afghanistan. Leggett said he could not comment on offensive counterterrorism operations because he was not given enough time to gather information and obtain the necessary clearance to release it publicly. The story has been updated.