ASWAN, Egypt — German officials have established direct contact with kidnappers of a 19-member tour group in Egypt after days of trying to negotiate through mobile phone calls between one of the captives and his wife, Egyptian and Sudanese officials said yesterday.

The kidnappers, who snatched the 11 Europeans and 8 Egyptians on Friday during a desert safari in Egypt, have taken their captives across the border into Sudan. Sudanese troops have located them and are keeping watch on their position, but are not moving against them for fear of endangering the hostages, a Sudanese Foreign Ministry spokesman said.

Germany, five of whose citizens are among the captives, has been negotiating with the kidnappers, who have demanded up to $15 million in ransom, according to Egyptian officials.

Until now, negotiations were taking place through two phone calls a day between the tour company’s Egyptian owner, who was among those kidnapped, and his German wife, who lives in Egypt, an Egyptian security official said.

He spoke on condition of anonymity because he was not authorized to discuss details of the talks.

The wife has been staying at the German Embassy in Cairo, according to Italian press reports. But until now there had been no sign the Germans were speaking directly to the kidnappers.

But the Egyptian security official said yesterday that German authorities had established direct contact. The contacts were also reported by the Sudan Media Center, a news agency with close links to the Khartoum government. Neither gave details on how the communications were taking place.

Germany has been silent on any negotiations, refusing to even confirm that it is conducting them.

“I ask you to understand that it won’t help anyone if we approach the press with any of the details,” a Foreign Ministry spokesman, Andreas Peschke, said yesterday. “I think we have a good reason to carry out our public relations in the way that we do.”

The identity of the kidnappers remains a mystery. They are believed to be desert tribesmen. Sudan said Tuesday it believes they are Egyptians. In one of the initial calls to his wife, however, the tour operator reportedly described the kidnappers as “African” in appearance.

The five Germans, five Italians, a Romanian, and eight Egyptian guides and drivers were abducted while visiting the Gilf al-Kebir, an isolated plateau some 550 miles southwest of Cairo in Egypt’s Western Desert. The site is little visited, with only a few hundred adventure tourists a year making the grueling desert journey, drawn by the location’s dramatic desert scenery and the rich troves of prehistoric art in the plateau’s numerous caves.