German Chancellor Angela Merkel will travel to Ankara next week for talks with Turkey's prime minister, her spokesman said Friday, as she seeks to cut the flow of refugees into the EU.

Merkel will meet with Prime Minister Ahmet Davutoglu on Monday to discuss "the further implementation of the EU-Turkey action plan" agreed in November to reduce the number of asylum seekers arriving in the bloc.

The huge flow of migrants and refugees to Europe via Turkey must be slowed, the interior ministers of France and Germany said Friday after inspecting registration facilities in Greece.

The goal "cannot just be to register arriving refugees and to relocate them equitably (but above all) to reduce the flow," German Interior Minister Thomas de Maiziere said at the close of the two-day visit.

Up to 20,000 Syrians were stranded on the Turkish border Friday after fleeing a major Russian-backed regime offensive near Aleppo where a new humanitarian disaster appeared to be unfolding.

Tens of thousands of civilians have joined an exodus to escape fierce fighting involving government forces who severed the rebels' main supply route into Syria's second city.

Russia on Thursday accused Turkey of actively preparing to invade Syria, saying it had spotted troops and military equipment on the border with the war-torn country.

"We have serious grounds to suspect Turkey is in intensive preparations for an armed invasion of the territory of a sovereign state -- the Syrian Arab Republic," the defense ministry said in a statement.

A Turkish appeals court on Thursday overturned the conviction of two police officers jailed for at least 10 years for beating to death a teenager in 2013 anti-government protests, local media reported.

The court overturned the verdict on "procedural grounds", the state-run Anatolia news agency reported, without elaborating.

Turkey on Thursday said that it had refused to allow a Russian reconnaissance plane to overfly its territory near Syria, citing a disagreement over the flight plan, as relations between the two countries hit a post-Cold War low.

The Turkish foreign ministry's statement came a day after Russia accused Turkey of breaching the Open Skies treaty by refusing the plane access.

An armed U.S. Predator drone crashed in Turkey on Wednesday after apparently suffering some kind of mechanical failure, military officials said.

Captain Lauren Ott of the U.S. Air Force's Europe command said the drone went down in an unpopulated area of southern Turkey at around 1:40 am local time (2340 GMT).

The basement of apartment block "23" in the the flashpoint town of Cizre in southeastern Turkey has become the focus of a bloody standoff as fighting rages on between security forces and Kurdish rebels.

More than two dozen wounded Kurds have been trapped in the cellar of the largely ruined building in the besieged town for almost two weeks, and pro-Kurdish lawmakers say fears are mounting for their lives.

Police on Tuesday arrested two men in western Turkey suspected of plotting a suicide attack, according to the Dogan news agency.

Officers found a machine gun, a grenade as well as explosives and ammunition in luggage belonging to the two men, who were detained at a bus station in the town of Soke, in Aydin province, the report said.

Syria's government has condemned alleged cross-border shelling by Turkish forces on Monday as a "blatant breach of international law", state media reported.

Late Monday, state news agency SANA quoted a source in the Syrian foreign ministry as condemning the reported artillery fire into northern Latakia province.