A Syrian passenger plane is seen after it was forced to land at Ankara airport on Oct. 10, 2012. The plane was forced to land in Ankara on suspicions that it was carrying weapons. (Adem Altan/AFP/Getty Images)

Turkish fighter jets forced a Syrian passenger plane to land in Ankara on Wednesday amid suspicions that it may have been carrying arms, exacerbating already high tensions with Syria that have raised fears that a wider war may be imminent.

The fears have prompted the United States to dispatch 150 troops to Jordan to help the authorities there formulate contingency plans for the crisis next door in Syria, Defense Secretary Leon E. Panetta said at a news conference in Brussels.

Turkish officials said the civilian Airbus 320 with 30 passengers on board was intercepted by F-16s as it entered Turkish airspace and was escorted to the capital’s Esenboga Airport shortly after 5 p.m. Hours earlier, Turkey had ordered all Turkish civilian aircraft to cease flights through Syrian airspace, apparently to prevent Syria from taking reciprocal action.

Turkish Foreign Minister Ahmet Davutoglu told Turkish television network TGRT that the plane had been forced down because it was carrying “non-civilian cargo” and “banned material.”

“There is information that the plane had cargo on board that does not meet the requirements of civil aviation,” he said in the interview in Athens. The Today’s Zaman newspaper later reported that Turkish authorities found military communication equipment and “parts that could be used in missiles” on the plane.

Russia, one of Syria’s staunchest allies, has in the past acknowledged supplying the Damascus regime with weapons and has blocked several efforts at the United Nations to impose an arms embargo.

Ankara and Damascus, long at odds over the bloody revolution in Syria, lurched closer to war a week ago after several Syrian shells exploded in a Turkish border village, killing five civilians and prompting Turkey to retaliate with barrages of mortar fire against Syrian targets.

Syria refused to apologize and instead denounced Turkey for allowing rebels battling the regime led by President Bashar al-Assad to transport weapons and funds across its border. Although mortar rounds fired during battles had accidentally strayed into Turkey on several previous occasions, Turkish officials said the incident last week was different because five shells struck a residential area almost simultaneously.

Over the next five days, at least five more Syrian shells exploded in Turkey, increasing suspicions that Syria was deliberately needling its neighbor in an effort to undermine Turkish Prime Minister Recep Tayyip Erdogan. Turkey reciprocated by firing mortar shells into Syria on each occasion, and it has reinforced its southern border with extra troops, artillery and fighter planes.

Earlier Wednesday, Turkey’s top general warned of harsher retaliation if more Syrian mortar shells land in Turkish territory.

“We responded, but if it continues, we will respond with greater force,” Chief of General Staff Necdet Ozel told Turkish media during a visit to the southern town of Akcakale, where the five civilians were killed.

The dispatch of the U.S. troops to Jordan, reported by the New York Times on Wednesday, marks the first American military deployment directly associated with the nearly 19-month-old Syria crisis, which has swamped neighboring states with refugees and risks igniting a regional conflict. The Local Coordination Committees, an opposition group, said 173 people were killed in Syria on Wednesday.

Most of the 150 U.S. troops are Army special operations forces, and some have been in Jordan for several months, Panetta said. They are helping Jordan monitor Syrian chemical and biological weapons sites and develop its own military capabilities “so that we can deal with all of the possible consequences” of the Syria war, he said.