The U.S. State Department and Pentagon ordered the families of U.S. diplomats and military personnel Tuesday to leave posts in southern Turkey due to "increased threats from terrorist groups" in the country.

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The two agencies said dependents of American staffers at the U.S. consulate in Adana, the Incirlik air base and two other locations must leave. The so-called "ordered departure" notice means the relocation costs will be covered by the government.

In a statement, the military's European Command said the step "allows for the deliberate, safe return of family members from these areas due to continued security concerns in the region."

.BREAKING NEWS: SECDEF authorized the ordered departure of all #military dependents from #Turkey. Learn more at https://t.co/QCqBJR70OD — U.S European Command (@US_EUCOM) March 29, 2016

The orders cover the Adana consulate, U.S. military dependents in Incirlik, Ismir and Mugla as well as family of U.S. government civilians at Ismir and Mugla. The State Department also restricted official travel to that which it considers "mission critical."

The move comes amid heightened security concerns throughout Turkey due to the ongoing fight against Islamic State militants in neighboring Syria and Iraq and was accompanied by an updated travel warning advising U.S. citizens of an increased threat of attacks. It also comes as Turkey's president is set to arrive in Washington to attend President Barack Obama's nuclear security summit.

"We understand this is disruptive to our military families, but we must keep them safe and ensure the combat effectiveness of our forces to support our strong ally Turkey in the fight against terrorism," the European Command statement said.

Incirlik is a critical base in the fight by the U.S.-led coalition against the Islamic State group, and includes strike aircraft, drones and refueling planes.

NEW: U.S. State Dept. issues travel warning for Turkey due to "increased threats from terrorist groups." pic.twitter.com/K6W35OhGyw — ABC News (@ABC) March 29, 2016

Turkey's decision last year to allow the coalition to conduct airstrikes with aircraft based at Incirlik shortened the time and distance required to conduct airstrikes in Syria and Iraq, compared with strikes flown from bases in the Persian Gulf area. And it increased the number of U.S. personnel at the base.

NATO's Allied Land Command is based at Ismir and there is a Turkish base at Mugla where some U.S. military personnel go for training and other missions.

It was not immediately clear how many family members would be affected in total. The Pentagon said the order would affect about 680 military family members and roughly 270 pets. The State Department and Pentagon had begun a voluntary drawdown of staff at the two posts last September after Turkey announced it would take a greater role in the fight against Islamic State militants.

US issues travel warning for Americans in #Turkey: USG staff restricted to "mission critical" activities in Izmir. pic.twitter.com/YrsJWOC5vE — Jon Williams (@WilliamsJon) March 29, 2016

At the time, military officials said they had recommended the voluntary departure from Incirlik because of specific calls by militants for lone wolf attacks against the air base.

On Monday, Secretary of State John Kerry met with Turkish Foreign Mevlut Cavusoglu. State Department spokesman John Kirby said the two discussed measures to secure the Turkey-Syria border and disrupt extremist networks.

According to a U.S. official, the decision to order families to leave stemmed from the ongoing assessment of security threats in Turkey. The official was not authorized to discuss the matter publicly so spoke on condition of anonymity.

The decision comes a day after Israel issued a new travel advisory for Turkey, warning its citizens to leave the country as soon as possible and avoid any traveling there.

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