UPDATE 1-Caltex Australia has unplanned diesel unit outage

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PERTH, April 15 (Reuters) - Caltex Australia Ltd (CTX.AX), the country's only listed oil refiner and marketer, said on Tuesday it has shut down a diesel hydrotreater unit at the 105,000 barrel per day Lytton refinery for urgent unplanned repairs.

Caltex spokeswoman Alison Badger said the unit has been shut down since early April but should resume production by end of the month.

Caltex said that as a result of the shutdown, diesel supplies in the southeast of Queensland state, where the Lytton refinery is located were experiencing some shortages.

Caltex said was making effort to bring in additional diesel supplies from other states and overseas to boost capacity at the Lytton distribution terminal.

A diesel cargo has been purchased to arrive at Lytton before the end of the month and the company was looking to get more prompt-delivery imports, Badger said.

"Supplies of diesel to service stations are being allocated on the basis of a limited percentage of the sites' usual requirements," Caltex said in a separate statement.

"This will mean that from time to time some Caltex service stations may be without diesel for a few hours until the next delivery can be made."

Caltex said petrol supplies have been unaffected.

(Reporting by Fayen Wong)