Update: 5 Killed in Violent Riots Over Koran Burning on U.S. Air Base in Afghanistan

KABUL, Afghanistan (The Blaze/AP) -- The controversy over the burning of Islamic holy books at a U.S. air base has turned violent (read the original report here). An Afghan official says two protesters have died in an exchange of gunfire during a riot outside an American base in eastern Afghanistan that also wounded two NATO troops.

The deaths raise to five the number of Afghans killed around the country during Thursday's protests over this week's Koran burnings. The chaos, which shows no signs of simmering, started earlier this week. On Tuesday, The Blaze reported:

More than 2,000 angry Afghans rallied Tuesday against the inadvertent burning of Korans and other Islamic religious materials during trash disposal at an American air base. They demanded to meet the country’s president over the issue and threatened to demonstrate again if their demand was not met.

U.S. Gen. John Allen, the top commander in Afghanistan, apologized and ordered an investigation into the incident, which he was “not intentional in any way.”

Here's Allen's apology:

President Obama, too, has commented on the matter. The Afghan president's office says it has received a letter from President Obama formally apologizing for the burning of Qurans at a U.S. military base in Afghanistan.

The statement from President Hamid Karzai's office says the U.S. ambassador delivered the letter on Thursday.

In the letter, which is quoted in the statement, Obama expresses his "deep regret for the reported incident" and offers his "sincere apologies."

According to the statement, Obama wrote: "The error was inadvertent; I assure you that we will take the appropriate steps to avoid any recurrence, to include holding accountable those responsible."

So far, this attempt to temper the situation has done little to stem the outrage. On Thursday, Governor Haji Mohammad Hassan says NATO and Afghan troops were firing in the air to disperse hundreds of protesters gathered in front of the base in Khogyani district in eastern Nangahar province.

Hassan says during the rioting, one man in an Afghan army uniform shot at NATO troops and seriously wounded two of them. The Taliban are seizing upon the opportunity to encourage violence among Afghans.

"The protest and shootings came as the Taliban called on Muslims to attack NATO military bases and convoys and kill its soldiers following the admission that NATO troops had incinerated Islamic religious material at Bagram Airfield," CNN reports.

Earlier, Afghan police shot and killed three protesters during two demonstrations in the north and south of the country.

On Wednesday, WFLA radio spoke with a woman named "Lisa" -- reportedly the mother of a soldier who is stationed at Bagram Air Force based. She described the current conditions on the base as a result of the protests:

"They don't have running water," she said. "Electricity is scarce, (and) they're on all sorts of drills and lockdowns."

Listen to Lisa's comments and her limited communications with her son, below:

Update: CBS News reports:

Two U.S. troops have been shot to death and four more wounded by an Afghan solider who turned his gun on his allies in apparent anger over the burning of Korans at a U.S. military base in Afghanistan, an Afghan official tells CBS News.

A statement from the International Security Assistance Force - Afghanistan, the international coalition in the country, confirmed that two troops were killed in Eastern Afghanistan on Thursday by "an individual wearing an Afghan National Army uniform." [...]

The source also said the shooting appeared to be motivated by the burning of Korans at the sprawling U.S. Bagram air base, north of Kabul, but he did not provide additional details as to what led him to that conclusion.