An explosion at a police compound in the southeastern Turkish city of Diyarbakir that killed three people on Tuesday was caused by a bomb planted by attackers in a tunnel under the complex, officials said.
Turkish authorities previously said the blast, which struck in the mainly Kurdish region days before a referendum on expanding President Tayyip Erdogan's powers, appeared to have been triggered during the repair of an armoured vehicle."It turned out that the explosion was the result of a terrorist attack. The attack was carried out through a tunnel dug from the outside. They dug a tunnel and placed the explosives in the ground," Interior Minister Suleyman Soylu told broadcaster Haberturk on Wednesday.
He did not say who was believed to be behind the blast, although Kurdish militants have regularly carried out similar attacks on police and military compounds in the southeast since a peace process with the state has collapsed in summer of 2015.
A statement from the Diyarbakir governor's office said the attackers dug a 30-metre tunnel from the basement of an adjacent building. Forensic investigations showed that about one tonne of explosives and diesel were detonated by timer, it said.
The death toll from the attack has risen to three from an initial one, the governor' office said - one officer and two civilians. Four wounded people were still in hospital.
Five people suspected of direct links to the incident had been arrested. Another 172 people "thought to be in relation with terrorists" were also detained, the statement said without giving details.
The attack came ahead of Sunday's referendum on changing the constitution and creating an executive presidency long sought by Erdogan. It also marks the first militant attack since the campaigning for the April 16 referendum officially started.
Turkey faces multiple security threats, including from Islamic State and Kurdish militants. The outlawed Kurdistan Workers Party (PKK), which took up arms against the state in 1984, is considered a terrorist organisation by Turkey, the United States and Europe.
