KABUL, Afghanistan — A bomb in a mosque killed a provincial governor Tuesday in the highest profile assassination in recent months, part of an intensified campaign to intimidate Afghanistan’s administration as it prepares for elections and the withdrawal of foreign troops after 12 years of war.

The bomb killed Gov. Arsallah Jamal of eastern Logar province as he delivered a speech at the main mosque in the provincial capital of Puli Alam to mark the Muslim holiday of Eid al-Adha. The attack also wounded 15 people, five of them critically, said his spokesman, Din Mohammad Darwesh.

Jamal was a close confidant and adviser to President Hamid Karzai, who strongly condemned that bombing, saying it was an attack “against Islam.”

“Terrorists and the Taliban working in the name of Islam carry out attacks that result in the killing of innocent Muslims. Surely it is not the act of Muslims, but those who have been hired to kill Muslims,” Karzai said.

He did not elaborate, but he has often blamed foreign interests, mostly in neighboring Pakistan, of being behind many of the high profile attacks against members of his administration in recent years.

No group has claimed responsibility, but it bore the hallmarks of the Taliban, which has been fighting Karzai’s administration and the foreign military presence in Afghanistan since the U.S. invasion in late 2001. The group has made attacking government officials a key part of its official military campaign this year.

In a message Monday timed for the Eid al-Adha holiday, the secretive leader of the Afghan Taliban, Mullah Mohammad Omar, called for his fighters to intensify their campaign against Afghan and NATO forces, and he urged all Afghans to boycott the April 5 election that will elect Karzai’s successor. All foreign military combat forces are to withdraw from Afghanistan by the end of 2014.

Logar, which is located just south of Kabul, was once a mostly calm province. But it has recently seen an influx of Taliban fighters and increased attacks against government forces.

Jamal, 47, was Karzai’s campaign manager during the 2009 presidential elections. He also was governor of Khost province until he was appointed to his current post in Logar in April.

A high-profile target, Jamal had survived a number of assassination attempts, including suicide bombings against his office in Khost in May and July 2009, and a suicide car bomb attack that targeted his convoy in August 2007.

At the scene of Tuesday’s mosque bombing, debris was scattered on the green prayer carpets where worshippers had knelt in prayer hours earlier. Blood spattered the gray marble walls.

Although details of the bomb have not been released, numerous officials have said it was planted somewhere inside a microphone stand in front of Jamal. Logar’s deputy police chief, Rais Khan Abbul Rahimzai, said an investigation was underway.

Sophisticated explosives have been used to kill government officials, including bombs in turbans and even inside people’s bodies.

Former Afghan President Burhanuddin Rabbani, the leader of a government-appointed peace council, was killed in his home in September 2011 by an insurgent posing as a Taliban peace envoy. The militant detonated a bomb in his turban as he kissed Rabbani in a traditional greeting.

The killing of Jamal was the highest profile attack against a Karzai confidant since December, when a suicide bomber posing as a peace messenger from the Taliban severely wounded Afghanistan’s intelligence chief, Asadullah Khalid. Karzai said both attacks were planned by insurgents in Pakistan.

The Taliban, believed to be based in Pakistan’s lawless tribal regions, have intensified attacks on government officials and members of Karzai’s administration.

In June, a Taliban suicide bomber struck outside Afghanistan’s Supreme Court, killing 17 people. In April, insurgents attacked a courthouse and government offices in Farah province, killing 46 people, including two judges, six prosecutors, administration officers and other working.

Nicholas Haysom, the deputy U.N. chief in Afghanistan, condemned the attack and said such bombings violate international humanitarian law.

“The U.N. mission reiterates its call for such attacks to cease immediately and for respect of the sanctity of protected religious places such as mosques,” Haysom said.

The wave of attacks since the NATO handover of security responsibilities to Afghan forces has led to a spike in casualties, both among Afghan forces and civilians. The U.N. has blamed insurgents for most of them.

Eid al-Adha is one of Islam’s most important holidays. Muslims around the world slaughter sheep, cows and goats during the four-day celebration, giving much of the meat to the poor. The holiday commemorates the readiness of the Prophet Ibrahim, known to Christians and Jews as Abraham, to sacrifice his son, Ismail, on God’s command.