Maroua, Cameroon (CNN) -- Nigeria's Boko Haram is responsible for kidnapping a French priest in neighboring Cameroon -- the same day the U.S. government labeled the group a terrorist organization -- said the governor of Cameroon's Far North region.
Though Gov. Fonka Awa Augustine ordered his region's border with Nigeria closed, it may be too late, as eyewitnesses reported seeing the armed militants cross into Nigeria on motorcycles after Wednesday's kidnapping.
"This is shocking," the governor said Friday. "All expatriates should restrict their movement in this region. They should stay within much secured areas and avoid visiting touristic sites."
The priest, Georges Vandenbeusch, was snatched from his parish church in Nguetchewe, about 11 kilometers (7 miles) from the Nigerian border, security officials said.
"Our Father Georges was kidnapped just a few minutes after celebrating holy Mass that night," Mbah Anatole Asah, a Christian in the parish, said Wednesday night.
Witnesses said they believed Vandenbeusch was targeted because he is French and Christian. Boko Haram has declared a "war on Christians" as it strives to spread a strict brand of Sharia law across northeastern Nigeria.
Boko Haram has not claimed responsibility for Vandenbeusch's abduction.
The abduction comes the same week that the Nigerian army killed seven Boko Haram militants and injured others during a firefight in the Damboa area of Borno state, about 115 kilometers (72 miles) from the Cameroon border. Soldiers also seized a pickup truck, two motorcycles, "large arms" and ammunition, according to a statement.
The army said it has recently intensified its patrols in the forested areas of Damboa and Gwoza, destroying Boko Haram camps, hideouts and vehicles.
Earlier this year, Boko Haram kidnapped a French family of seven, including four children, in Dabanga near the Nigerian border. They were released unharmed days later.
Security analysts in Cameroon blame the kidnappings on the lawlessness in north Cameroon and poor security along its porous border with Nigeria. Witnesses said the unarmed Cameroonian border patrol fled when the heavily armed militants approached the border Wednesday night.
"The security is weak. It is very weak," legal expert Ngalim Bernard Yongabi said.
The kidnappers left bullets in the priest's home, state radio reported. Security officials said they believe the bullets are a sign of Boko Haram's willingness to fight as Nigerian President Goodluck Jonathan seeks this month to extend a state of emergency in the northeast. The state of emergency was declared in May.
Boko Haram militants do not have the financial capacity to conduct large-scale military operations, Yongabi said.
"Their activities in northern Nigeria have been stoked by the Nigerian military. They are now exploiting the weak security in Cameroon to hibernate in Cameroon and take foreigners hostage," he said.
Fonkam Azu, governor of Cameroon's northern region of Maroua, said specialized military forces have been sent to secure the border with Nigeria.
Dozens of foreigners, including U.S., French and British citizens, have been pulled back from dangerous areas in northern Cameroon into more secure cities.
In freezing the group's assets and placing travel bans on Boko Haram's members this week, the U.S. State Department said the organization is responsible for thousands of killings since 2009. Human rights groups put the number at 3,000.
Boko Haram's leader, Abubakar Shekau, has a $7 million bounty on his head.
The terror outfit, whose name means "Western education is sacrilege" in the Hausa-Fulani language, has attacked numerous targets since forming in the late 1990s, killing and kidnapping Westerners and bombing schools, churches and mosques, according to the U.S. National Counterterrorism Center.
Recently, Boko Haram was blamed in an August mosque attack in Nigeria's Borno state that killed 44 worshippers, September attacks in Benisheikh that left 160 civilians dead, many of them Muslim women and children, and a September assault on an agriculture school in which 50 students were killed in their dorms while they slept.
The United Nations has said it wants to try members on war crimes after an attack on a wedding party that killed 30 people.
An estimated 8,000 Nigerians have fled to Cameroon to escape the violence, while another 5,000 people have been internally displaced, the United Nations says.
CNN's Eliott C. McLaughlin and Greg Botelho contributed to this report.