ISTANBUL, Dec 5 (Reuters) - Turkey still expects an apology and compensation for nine Turkish activists killed on a Gaza-bound ship this year, despite its offer of help to Israel in battling forest fires, its prime minister said on Sunday.

Israeli Prime Minister Benjamin Netanyahu telephoned Prime Minister Tayyip Erdogan on Friday to thank him after Turkey sent fire-fighting planes to help battle forest fires in northern Israel that killed 41 people.

It was the first conversation between the two men since Israeli commandos killed the nine Turkish activists while storming their boat, the Mavi Marmara, that was bringing supplies to the blockaded Gaza Strip.

Netanyahu said Turkey's gesture would be an opportunity to improve ties between the erstwhile allies. But Erdogan said the help on the fires was purely humanitarian.

We would never stand by when people are being killed and nature is being destroyed anywhere in the world, Erdogan said in comments broadcast live by CNN Turk. No one should try to interpret this any differently.

Now some are coming out and saying, 'Let's begin a new phase.' Before that, our demands must be met ... Our nine brothers martyred on the Mavi Marmara must be accounted for. First an apology must be made and compensation must be paid.

Israel had enjoyed close military and commercial ties with Muslim but secular Turkey since the 1990s.

Netanyahu's government has since accused Erdogan, a devout Muslim, of turning away from Western allies and embracing Iran and other Islamic states.

Erdogan criticised Israeli conduct during strikes on Gaza in late 2008 and early 2009, which followed Turkish efforts to mediate between Israel and Syria in failed peace talks. (Writing by Ayla Jean Yackley; editing by Myra MacDonald)