ANKARA/BERLIN (Reuters) - Turkish authorities detained four people in an investigation into a potential threat against British and German diplomatic missions but found no links to any terrorist groups, a Turkish official said on Friday.

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The investigation was prompted by intelligence about a potential Islamic State plot against the embassies, the official said.

“Four people were detained in relation to a potential act against the two embassies. Security remains at the highest level. We continue to cooperate closely and share information with the foreign missions,” the official said.

Three of the suspects were detained in the capital Ankara and one of them in Istanbul, state-run Anadolu Agency said.

Britain shut its embassy in Ankara on Friday for what its foreign office said were security reasons, without giving further details.

A spokesman for Germany’s foreign ministry confirmed its diplomatic offices were closed this week, citing both a four-day public holiday in Turkey and information, which he described as “not completely verifiable”, about a potential attack.

“We take such leads seriously,” the spokesman told reporters at a regular news conference in Berlin. “So we decided to keep our diplomatic missions and German schools in Turkey closed this week. It was a precautionary measure.”

He said the government would make a decision after the weekend on whether the missions would reopen on Monday.

Government offices and financial markets were closed in Turkey from Monday to Thursday for the Muslim Eid al-Adha holiday.

Turkey has suffered a series of suicide bombings and attacks by Islamic State and Kurdish militants over the past year. It launched its first major military incursion into Syria last month to push the jihadists away from its border and prevent Kurdish fighters from seizing territory as they retreated.

In its latest travel advice, Britain’s foreign office urged against travel to within 10 km (6 miles) of the Syrian border and to Diyarbakir, the largest city in the mainly Kurdish southeast, hit by violence after a ceasefire with the outlawed Kurdistan Workers Party (PKK) broke down last year.