DIYARBAKIR, Turkey (Reuters) - Turkish authorities detained 13 people including municipal officials on Wednesday on suspicion of trying to assassinate a senior politician by planting explosives at a cemetery where his relatives are buried, security sources said.

Police found 640 kilograms (1,411 pounds) of explosives at a cemetery plot for relatives of Mehdi Eker, deputy chairman of the ruling AK Party and a former agriculture minister, in the largely Kurdish southeastern province of Diyarbakir, they said.

The security sources said the explosives were detected a day before Eker was due to make an annual visit to the cemetery ahead of last week's Eid al-Adha holiday.

Some of the 13 people detained were municipal officials in Diyarbakir province, they added, giving no further details.

The city of Diyarbakir is the largest in the southeast. The region has been scorched by waves of violence since a ceasefire between the Turkish state and the outlawed Kurdistan Workers Party (PKK) fell apart last year.

The government has removed two dozen elected mayors in the southeast this month over suspected links to militants. The pro-Kurdish opposition Peoples' Democratic Party (HDP), the third largest in Turkey's parliament, has decried the move as an "administrative coup".

Security sources also said a Turkish village guard was killed on Wednesday in clashes with Kurdish militants in the southeastern town of Siirt, and that an aerial operation was under way against the insurgents.

The fighting broke out in a rural district of the town, they said. Village guards are residents armed and paid by the state to protect their communities. They are frequent targets of PKK militants.

More than 40,000 people, many of them Kurds, have died since the autonomy-seeking PKK first took up arms against the government in 1984.

(Writing by Tuvan Gumrukcu; Editing by David Dolan and Mark Heinrich)