U.S. military forces in Afghanistan (search) are conducting an "aggressive search" for a Navy SEAL who has been missing since June 28, a commander on the ground told FOX News.

"It's nighttime and a lot happens for us at night," the commander said. When asked if hopes were fading for finding the SEAL alive, he said, "Oh, no, I would not characterize it that way at all."

On Thursday a purported Taliban spokesman reiterated a claim that his group is holding a missing U.S. commando and said that insurgent leaders had decided to kill him. No proof was offered to back up the claim.

The U.S. military had no comment on the latest claim, saying only that they are making every effort to locate the commando.

The Taliban spokesman, Mullah Latif Hakimi (search), has said previously that the Taliban are holding the commando, who has been missing in Afghanistan for 10 days. But his information has in the past frequently proven exaggerated or untrue, and his exact tie to the Taliban leadership cannot be independently verified.

The search is on to find the final member of an elite four-man Navy SEAL (search) commando team. One SEAL has been rescued, while the bodies of two others were recovered Monday and taken to the main U.S. base in Afghanistan, at Bagram (search), a U.S. military statement said. A transport helicopter sent in to rescue the four was shot down the day the team went missing, killing all 16 U.S. servicemen aboard.

The Department of Defense identified the two SEALS found dead as Petty Officer 2nd Class Danny P. Dietz, 25, of Littleton, Colo.; and Lt. Michael P. Murphy, 29, of Patchogue, N.Y.

Dietz was assigned to SEAL Delivery Vehicle Team Two, Virginia Beach, Va., while Murphy was assigned to SEAL Delivery Vehicle Team One, Pearl Harbor, Hawaii.

Both died during counter-terrorism operations in Kunar Province, Afghanistan. Coalition forces fond the service members while conducting a combat search-and-rescue operation July 4 in Kunar Province. The sailors' whereabouts had been unknown since June 28.

"We're ... doing everything we can to find the last of the four SEALs. And it's a real priority, and something the president asked to get briefed on this morning," U.S. National Security Adviser Stephen Hadley told reporters aboard Air Force One.

Another U.S. military spokesman, Col. James Yonts, would not go into details about the search to reporters. "We are very hopeful that we will recover this individual back into our care soon. We are working this very hard," he told reporters in Kabul.

He said the U.S. military has 300 troops in the area as well as numerous aircraft.

A U.S. military statement said the sole rescued serviceman was receiving medical treatment for "non-life-threatening injuries" at the Bagram base.

The commander who spoke to FOX News on condition of anonymity said the SEAL team found itself in a heavy firefight with a group of Taliban or Al Qaeda fighters when it called for backup.

The SEALs started moving out of the area and down a ravine when they came under more heavy small arms and rocket propelled grenades from another direction. The rescued SEAL remembers seeing two of his colleagues being shot — although he didn't know whether the shots were fatal, according to the commander.

The one SEAL was knocked unconscious from the concussion of an explosion nearby. When he woke up, it was night and he didn't see anyone. He then went to a pre-assigned checkpoint to get out of the area, the commander said.

Rebels Attack U.S. Medical Team

Elsewhere in Afghanistan, rebels attacked a U.S. military medical team as it was helping villagers in the same region of eastern Afghanistan (search) where a U.S. airstrike that killed up to 17 civilians sparked sharp criticism from the government, the military said Wednesday.

No one was wounded in the assault Tuesday on the medical team near the town of Asadabad in Kunar province (search), a military statement said. U.S. forces used mortars to respond and the insurgents fled.

"It's incredible to us that the enemy would attack our forces while we are providing innocent Afghans with health care," U.S. military spokesman Lt. Col. Jerry O'Hara said.

The airstrike last Friday also was in Kunar and targeted a known terrorist base, the U.S. military said, but an Afghan government spokesman said the deaths of the civilians, including women and children, could not be justified.

It marked unusual criticism from the government of President Hamid Karzai (search), often viewed by critics as an American puppet. The United States provides security for the president as well as hundreds of millions of dollars a year in aid to Afghanistan.

The reprimand also highlighted Afghan government concern that deadly mistakes could erode public support for the U.S. presence here. In the past, Karzai's government has expressed interest in a long-term U.S. military presence in the region as Afghanistan recovers from nearly a quarter-century of war.

The air strike that killed civilians targeted a house in the same area. The number of people killed was still unclear, but "roughly half" may have been civilians, while the rest were Taliban or Al Qaeda fighters, Pentagon spokesman Bryan Whitman said Tuesday.

U.S. forces described the house as "a known operating base for terrorist attacks ... as well as a base for a medium-level terrorist leader."

"We deeply regret any loss of civilian life in the course of military actions," State Department spokesman Sean McCormack said.

Pentagon spokesman Lawrence Di Rita said the U.S. military takes "great strides" in trying to be precise when targeting combatants.

"But these things do occur and we obviously regret when they do. And we'll investigate to be able to determine what may have happened and how it can be avoided in the future," he said.

Jawed Ludin, Karzai's chief of staff, said "there is no way ... the killing of civilians can be justified."

An initial U.S. air strike destroyed a house, and as villagers gathered to look at the damage, a U.S. warplane dropped a second bomb on the same target, killing 17 people, including three women and children, Kunar provincial Gov. Asadullah Wafa said.

He said it was unclear who was killed in the initial attack on the tiny village of Chechal.

FOX News' Bret Baier, Nick Simeone and The Associated Press contributed to this report.