Security forces said on Friday that Turkish bomb-disposal experts successfully disabled an explosive device in a vehicle caught overnight near a government building in southeast Turkey.

The series of bomb attacks Turkey has been witnessing incited security warnings in major cities.

The vehicle was found with 150 kg (331 lb) of explosives in the town of Hani in the mainly Kurdish region’s Diyarbakir province, the sources said. Police were probing security cameras in the area as part of the investigation.

Kurdish militants on Thursday claimed a suicide bombing in Ankara that was perpetrated by a male and a female from the Kurdistan Workers Party (PKK) killing 37 people this week. It also warned of further attacks, while Germany shut down its diplomatic missions and schools in Turkey.

Germany’s foreign ministry issued a statement advising caution in Ankara, Istanbul and other major Turkish cities. Foreign Minister Frank-Walter Steinmeier said on Thursday that he had ordered German institutions in Turkey to close their doors, “because protecting German citizens and the people working and learning in these establishments must now take precedence.”

The U.S. embassy in Ankara issued a statement overnight saying its citizens “should be mindful of their security precautions”, noting Kurdish New Year (Newroz) celebrations taking place this weekend and saying large events can turn hostile and escalate into violence.

“The U.S. Embassy also reminds individuals that terrorist organizations have targeted transportation hubs, Turkish government facilities, and public spaces in the recent past,” it said.

Last Sunday’s suicide bombing was the second in a month in the heart of Ankara claimed by the TAK militant group, bringing about a dangerous new stage in Turkey’s war with Kurdish militants as deadly attacks spread to its biggest cities well beyond the southeast where conflict is usually focused.