Kabul, Afghanistan (CNN) — Afghan President Hamid Karzai condemned a suicide bombing Monday at a military airfield, the latest incident in a spike in violence after the burning of Qurans by NATO troops last week.

At least nine people were killed and 12 wounded in the early-morning explosion near the front gate of the NATO-led International Security Assistance Force base at Jalalabad airport in eastern Afghanistan, according to Gen. Abdulla Hazim Stanikzai, the provincial police chief.

There were no NATO casualties. The Taliban insurgency said the attack was in retaliation for the Quran burning and said it hoped the attacks will continue “with the anger of the public.”

Another attack of “some significance” was reported later Monday in Naranghar province, near the Pakistani border, said Lt. Cmdr. James Williams, an ISAF spokesman.

A statement from the Taliban said its fighters also attacked U.S. troops and border police in southern Naranghar on Monday evening, claiming to have inflicted a dozen deaths on the U.S. and Afghan force while losing five of their own. But Williams said that while some insurgent casualties had been reported, there were no deaths among allied troops.

The Qurans that were burned were among religious materials seized from a detainee facility at Bagram Airfield last week. U.S. President Barack Obama apologized to Karzai last week, calling the burning an inadvertent error.

In a statement issued on the bombing Monday, Karzai condemned the “inhuman and un-Islamic” act and urged that “the ruthless enemy would earn nothing but growing public hatred and punishment before Allah, the Almighty.”

Gen. John Allen, commander of NATO and U.S. forces in Afghanistan, said insurgents tried to attack the ISAF installation and failed, instead taking more innocent lives.

The Taliban also claimed Monday to be behind the poisoning of food at a dining facility at Forward Operating Base Torkham, near the Afghanistan-Pakistan border. It too was a retaliatory attack, the group said.

ISAF confirmed that food at the base appeared to have been contaminated over the weekend, though it was unclear whether it was deliberate.

“Nobody got sick. A dining facility worker came to his leaders at the FOB and said that something had been poisoned,” said Maj. David Eastburn, an ISAF spokesman.

“The dining facility was shut down, and we brought in environmental health, who found traces of chlorine bleach in the coffee and fruit. Soldiers are now eating pre-prepared rations, and no one was affected. There is a full investigation that is narrowing down who was responsible.”

Capt. John Kirby, a Pentagon spokesman in Kabul, said it’s not clear whether the incident was a deliberate attempt to poison troops or “was just inadvertent, perhaps using more Clorox in the cleaning process than they should have.”

The Taliban has frequently exaggerated its claims or claimed responsibility for attacks that later turned out to be the work of another group.

Even so, Monday’s bombing and news of the contaminated food come on the heels of a week of violent protests over the Quran burning. The violence has left at least 39 people dead, including four American soldiers, and hundreds more wounded.

In northern Kunduz province over the weekend, protesters attacked a police chief’s office and a U.S. military base, authorities said. Some threw hand grenades at the base, known as Combat Outpost Fortitude, with resulting blasts wounding seven U.S. personnel believed to be Special Forces members, they said.

Demonstrations outside the United Nations office in Kunduz on Saturday left four civilians dead and prompted the U.N. mission there to say Monday that it is temporarily relocating its international staff.

Two U.S. soldiers were gunned down last week at a base in eastern Afghanistan by a man wearing an Afghan National Army uniform.

Allen pulled military advisers from Afghan ministries after Saturday’s shooting deaths of two other U.S. officers inside the heavily secure Ministry of Interior. Authorities are searching for the suspect, identified by Afghan police as a junior officer in the ministry’s intelligence department.

The suspect had been fired by the Interior Ministry but rejoined the intelligence services as a driver a couple of months ago, a senior Afghan counterterrorism official said Monday.

“We do not know how he was allowed into the office, as the command and control center requires a password for access,” said the official, who is not authorized to speak to the media about the topic. “There is something fishy there.”

The official said he believed that the gunman used a silencer on his weapon, as no one heard the gunshots. He said he doubts that an angry exchange led to the shooting, because the “way he entered was not accidental.”

Kirby said it’s not clear whether the shooting was linked the the Quran burning.

“We don’t know what the motivation was behind the murders, and we don’t know all the facts surrounding how this individual got into this space and frankly was able to get out as quickly and apparently as easily as he did,” Kirby said Monday.

Allen has told his commanders he will not authorize the return of personnel to Afghan ministries until new security measures are in place and working, according to an official who has access to the latest intelligence and is involved in administration discussions but declined to be identified because of the sensitive nature of the situation.

The religious materials, including Qurans, were removed from a detainee center library at Bagram Airfield because they had “extremist inscriptions” on them and there was “an appearance that these documents were being used to facilitate extremist communications,” a military official said.

The ensuing attacks have put pressure on already strained U.S.-Afghan relations at a time when the United States is working to reduce troop levels and transition security as part of its plan to withdraw by 2014.

Pentagon officials on Monday acknowledged the significance of the attacks but denied they are affecting the U.S. or NATO mission there.

“These events, they’re troubling. They’re worrisome. They’ve gotten everybody’s attention,” Kirby said. “Yes, tension is high here in Kabul right now, but across the country at large, the mission continues, and we’re seeing the protest activity decline.”

The number of protests in Afghanistan has gone from 24 on Saturday to three on Monday, only two of which were because of the Quran burning, Kirby said.

CNN’s Barbara Starr and Chelsea J. Carter contributed to this report.