A wave of Kurdish rebel attacks targeting police and soldiers in Turkey's mainly Kurdish southeast have killed at least 12 people, as country still deals with the aftermath of a failed military coup attempt that threatened the government.

Officials said rebels of the Kurdistan Workers' Party, or PKK, launched simultaneous bomb attacks targeting police vehicles in the city of Diyarbakir and the town of Kiziltepe, killing eight people, while four soldiers were killed in a separate attack near the border with Iraq hours earlier.

The attack in Kiziltepe was caused by a roadside bomb that went off as a police bus was passing by.

Three people were killed and at least 25 others were wounded there, including at least five children aged between two and five, said an official, who spoke on condition of anonymity in line with government regulations.

At the same time, a car bomb explosion targeting police in a historic part of the city Diyarbakir killed at least five civilians and wounded 12 others, the Diyarbakir governor's office said.

The explosion occurred at a security checkpoint at a bridge over the Tigris river.

The attacks came hours after an earlier attack, also blamed on the PKK, killed four soldiers and injured nine others near the border with Iraq.

The private Dogan news agency said that attack targeted military vehicles and was carried out with improvised explosives as well as rockets fired from northern Iraq.

Clashes between the PKK and Turkey's security forces resumed last year after a tenuous cease-fire collapsed and the PKK has frequently targeted police or military with roadside explosives or car bombs.

Wednesday's attacks, however, came as the country is still reeling from a violent coup attempt on July 15 that killed at least 270 people.

The government has blamed the failed coup on the supporters of US-based Muslim cleric Fethullah Gulen and has embarked on a sweeping crackdown on his followers.

The country is also combating the Islamic State group, whose militants have carried out a series of bloody attacks in Turkey in the past year.

US Secretary of Defence Ash Carter said in a statement Wednesday that the US stands "shoulder to shoulder" with its Turkish ally in the wake of the attacks.

"The United States remains committed to cooperating closely with Turkey - bilaterally, within the Counter-ISIL Coalition, and within NATO - in order to defend our nations against common threats," he said. Earlier this week, PKK commander Cemil Bayik threatened attacks against police in Turkish cities, according to media reports.

Since hostilities with the PKK resumed last summer, more than 600 Turkish security personnel and thousands of PKK militants have been killed, according to the state-run Anadolu Agency. Human rights groups say hundreds of civilians have also died.

Turkey and its allies consider the PKK a terror organisation.