Security for foreign instructors was increased after an American teacher was shot to death while jogging in Benghazi, amid fears that the death was not an isolated attack but rather one of an increasing number of targeted killings by Islamic militants or other gunmen with a strong presence in the volatile eastern Libyan city.

Ronald Thomas Smith II's body was found near the residential compound that housed him and other Benghazi International School teachers in an upscale neighborhood. He had been at school in the morning but went home to change his clothes and go jogging at midday, according to the school's director Adel al-Mansouri. The area is also the site of the U.S. diplomatic mission, where the U.S. ambassador and three other Americans were killed last year.

The United States, viewed by many Libyans as a protector who led NATO airstrikes that helped rebels oust dictator Moammar Gadhafi in 2011, has nonetheless become an enemy to Islamic militants who have flourished in the security vacuum, particularly in eastern Libya.

Five days before Smith's killing, al-Qaida's American spokesman Adam Gadahn called upon Libyans to attack U.S. interests everywhere as revenge for the abduction by U.S. forces of an al-Qaida suspect off the streets of Tripoli in October.

The school is located nearly 10 kilometers (six miles) outside the city and has about 600 students. School officials declined to give a breakdown about the number of Americans and other foreigners at the school for security reasons.

Smith, 33, who graduated in 2006 from the University of Texas in Austin with a master's degree in chemistry, moved to Benghazi with his wife, Anita, and young son a year and a half ago. His wife and son had gone home for Christmas, but he stayed behind to help students with final exams for the semester.

During his years in Texas, he was active in the Austin Stone Community Church, fulfilling what friends said was Smith's strong Christian beliefs.

Dozens of Egyptian Coptic Christians and others including South African, Swedish and American nationals have been detained by militias over accusations of spreading Christianity. In one incident in March, a Coptic Christian died, reportedly under torture, while held over accusations of proselytizing.

Spreading Christianity is a crime in the predominantly Muslim North African county.

The United States called on Libya to investigate Smith's death. Libya's Foreign Ministry said in statement that it was launching a probe, but authorities could not be reached for comment about suspects or other details. The central government holds little sway in Benghazi, which has an independent streak and is largely ruled by armed groups that sprang up after fighters refused to give up their arms following the 2011 revolution.

Benghazi, which was the birthplace of the Libyan revolution, has been struck by series of targeted killings of judges, activists, journalists, policemen and army officers. The city and the eastern region are hotbed of Islamic militia groups including Ansar al-Shariah which was blamed for the attack on US mission.

There has recently been a public backlash against militias throughout Libya, and they have clashed with armed residents and the security forces in Benghazi. But there is little sign yet that the government has the strength to dislodge them.

The United States pledged to train Libyan troops to help strength the army badly needed to restore security after the country has fell in hands of out-of-control militias, who originated in the rebel forces that fought longtime dictator Gadhafi's forces in eight-month civil war in 2011.

Al-Mansouri said the motive for Thursday's attack was unclear as the investigation was ongoing.

"We don't know if the killing was a terrorist attack or attempted theft," said al-Mansouri. Al-Mansouri also expressed concern the investigation could be tarnished because of the high number of police and prosecutors with ties to militia groups that may be to blame.

Al-Mansouri said the Benghazi International School has about 30 foreign teachers, including Americans, Britons and Australians. Six British teachers had been scheduled to join the school in January, al-Mansouri said, adding he didn't know if they still would do so after the attack.

More security guards were sent to the residential compound and teachers were to be accompanied at all times, al-Mansouri said, although he insisted the faculty would not be intimidated. "We have a message that we want to deliver to the next generations," he said in a telephone interview.

Abdullah al-Zaidi a former security official of the Joint Operation Room said that he doesn't rule out the possibility that it is a "terrorist attack."

"Sadly, those trying to send a message to the United States are only harming Benghazi," he said, adding, "the teacher was known as a very nice and generous person who didn't have any certain biases." He said that the day Smith was shot dead was a "bloody day" that witnessed several others killings like a senior officer and three soldiers in separate incidents.


Associated Press writer Maggie Michael in Cairo contributed to this report.