UPDATE 1-BASF to cut 3,700 jobs as part of Ciba takover

* To close or sell up to 23 of 55 Ciba sites

* Aims for 400 mln eur in annual synergies

* Sees 500 mln eur in total cash expenses from integration

* Shares up 0.1 percent

(Adds details, background)

FRANKFURT, July 6 (Reuters) - BASF (BASF.DE) plans to cut 3,700 jobs as part of the integration of Swiss rival Ciba and may sell or close as many as 23 of Ciba's 55 sites, it said on Monday.

That is the equivalent of around 28 percent of Ciba's 13,000-strong headcount, but some cuts will affect BASF staff, a spokeswoman said.

In its first detailed statement on the repercussions of the takeover, BASF said it aimed to generate synergies of at least 400 million euros ($559.1 million) per year from 2012 and that by the end of next year savings should amount to approximately 300 million euros.