ANKARA, March 25 (Reuters) - Turkey has taken delivery of six Heron drone aircraft from Israel and expects the remaining four to arrive by the end of April, Defence Minister Vecdi Gonul said on Thursday.

NATO member Turkey and Israel signed an agreement in 2005 for the procurement of 10 of the unmanned aircraft, used primarily for surveillance.

Israel has trained the Turkish personnel who will operate the drones and the first tests also were conducted there, Gonul told reporters at parliament. He did not say when the first six aircraft arrived in Turkey.

Delays in the $185 million project and a diplomatic row between regional allies Turkey and Israel had sparked speculation that the deal could be canceled.

Muslim Turkey has criticized Israel's Palestinian policies, especially the Gaza offensive it launched in December 2008.

Israeli defense manufacturer Elbit, Air Israel Aerospace Industries (IAI) and Turkish Aerospace Industries (TAI) are partners in the venture.

(Reporting by Pinar Aydinlip; writing by Ayla Jean Yackley; Editing by Michael Roddy)