A mortar round, apparently fired from Syria, crashed in a field in Turkey overnight close to a refugee camp housing thousands of Syrians along the border but there were no casualties, Turkish state media reported on Monday.
The incident, which could not immediately be confirmed by Turkish officials, would mark the first reported instance of spillover from Syria's civil war in Turkey in several weeks.
NATO troops have begun deploying Patriot defence missiles in Turkey - a supporter of rebels fighting to topple Syrian President Bashar al-Assad - against a potential attack from its southern neighbour.
The mortar was reported to have struck an olive grove in the village of Akcabaglar, 3 km (2 miles) from the Kilis refugee camp located next to the Oncupinar border crossing, state-run Anatolian news agency said on its website.
Nobody was injured by the mortar, which dug out a crater roughly 8 metres wide and 1.5 metres deep, it said.
A Syrian government warplane bombarded an insurgent position in the Syrian town of Azaz on Sunday, only 10 km (6.2 miles) from the Oncupinar gate.
Turkey has been bolstering security along its 910-km (565-mile) border with Syria and has responded in kind to gunfire and mortars hitting its territory. Five Turkish civilians were killed in October when a Syrian mortar struck their house in Akcakale, a border town in Sanliurfa province east of Kilis.
The Netherlands, Germany and the United States are sending two Patriot missile batteries and up to 400 troops each to Turkey after Ankara asked for NATO's help to increase security.
The missiles, to be stationed around three southeastern Turkish cities, are expected to be operational by the end of the month.