Updated

Afghan police on Thursday fired shots in the air to disperse hundreds of protesters who tried to break into an American military base in the country's east to vent their anger over this week's Koran burning incident.

The fresh violence came one day after clashes between Afghan troops and protesters broke out in the capital and in three eastern provinces over the incident, leaving at least seven people dead and dozens wounded.

The Afghan Interior Ministry said Wednesday the deaths occurred in the Afghan capital of Kabul, in the eastern city of Jalalabad, and in the provinces of Logar and Parwan.

It said four of the dead were killed during a protest in Parwan.

The ministry said security guards at a U.S. base outside Kabul killed one man, while one man each was killed during protests in Jalalabad and Logar.

The American embassy in Kabul, Afghanistan is on lockdown as protests rage in multiple Afghan cities over an incident the U.S. says was inadvertent burning of Muslim holy books at a military base.

"The Embassy is on lockdown; all travel suspended," the embassy announced on its Twitter page Wednesday. "Please, everyone, be safe out there."

The embassy later released an official security announcement, saying U.S. citizens should remain vigilant and avoid areas where westerners congregate.

"We wish to remind U.S. citizens that past demonstrations in Afghanistan have escalated into violent attacks on Western targets of opportunity," the statement said. "U.S. citizens are therefore urged to avoid the areas of demonstrations if possible, and to exercise caution if within the vicinity of any demonstrations, spontaneous or planned."

On the outskirts of the capital city of Kabul, security forces fired volleys of gunshots into the air to disperse hundreds who had gathered outside a housing complex for foreigners. Angry demonstrators set a fuel truck ablaze outside the complex, on a main highway linking the Afghan capital with the eastern city of Jalalabad.

"Death to America," chanted the angry protesters and automatic weapons fire could be heard, but it was unclear if Afghan security forces or camp guards were firing.

The city's police chief Mohammad Ayub Salangi arrived at the scene with hundreds of reinforcements in an effort to bring the crowd under control.

A doctor at Kabul's Wazir Akbar Khan hospital said at least 10 protesters had been brought to the hospital with gunshot wounds. The doctor, who spoke on condition of anonymity because he was not authorized to talk to the media, said one of the wounded was in critical condition.

Several miles away, hundreds were also gathered outside Camp Phoenix, a U.S. military base, and were hurling rocks at the installation, said Kabul provincial police spokesman Ashmatullah Stanekzai. There were reports that shots were also heard near Camp Phoenix.

Stanekzai said another smaller and peaceful demonstration with just over 100 people was taking place in western Kabul near the capital's university.

Police in eastern Jalalabad city said that thousands were gathering in parts of that city to demonstrate against the incident.

The U.S. military apologized Tuesday for the burning of books, including Korans, that had been pulled from the shelves of a detention center library adjoining Bagram air base because they contained extremist messages or inscriptions.

The White House later echoed military officials and said the burning was an accident.

"We apologize to the Afghan people and disapprove of such conduct in the strongest possible terms," they said in a statement quoted by the embassy on Twitter. ""This does not reflect the great respect our military has for the religious practices of the Afghan people."

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

"These kinds of incidents, when they do occur, will be corrected in the fastest and most appropriate manner possible," Allen said in a statement quoted by the embassy on Twitter. "We've been dying alongside the Afghans for a long time because we believe in them, and we want to give them a bright future."

Allen thanked the local Afghans "who helped us identify the error, and who worked with us to immediately take corrective action."

"We are thoroughly investigating the incident and are taking steps to ensure this does not ever happen again," he said in a statement.

The incident stoked anti-foreign sentiment that already is on the rise after nearly a decade of war in Afghanistan and fueled the arguments of Afghans who believe foreign troops are not respectful of their culture or Islamic religion.

Ahmad Zaki Zahed, chief of the provincial council, said U.S. military officials took him to a burn pit on the base where 60 to 70 books, including Korans, were recovered. The books were used by detainees once incarcerated at the base, he said.

"Some were all burned. Some were half-burned," Zahed said, adding that he did not know exactly how many Korans, the Muslim holy book, had been burned.

Zahed said five Afghans working at the pit told him that the religious books were in the garbage that two soldiers with the U.S.-led coalition transported to the pit in a truck late Monday night. When they realized the books were in the trash, the laborers worked to recover them, he said.

"The laborers there showed me how their fingers were burned when they took the books out of the fire," he said.

Afghan Army Gen. Abdul Jalil Rahimi, the commander of a military coordination office in the province, said he and other officials met with protesters, tribal elders and clerics to try to calm their emotional response. "The protesters were very angry and didn't want to end their protest," he said.

One protester, Mohammad Hakim, said if U.S. forces can't bring peace to Afghanistan, they should go home.

"They should leave Afghanistan rather than disrespecting our religion, our faith," Hakim said. "They have to leave and if next time they disrespect our religion, we will defend our holy Koran, religion and faith until the last drop of blood has left in our body."

Later, however, the protesters ended the rally and said they would send 20 representatives from the group to Kabul to talk with Afghan parliamentarians and demanded a meeting with President Hamid Karzai, Rahimi said.

The governor's office in Kandahar province in southern Afghanistan called the incident a "shameful move by some stupid individuals."

In April 2011, Afghans protesting the burning of a Koran by a Florida pastor turned deadly when gunmen in the crowd stormed a U.N. compound in the northern city of Mazar-e-Sharif and killed three staffers and four Nepalese guards.

The Associated Press contributed to this report.