ZURICH, June 12 (Reuters) - - FIFA president Sepp Blatter has expressed grave concern over reports that several Palestine players have been illegally detained in Israel.

Blatter had written to the Israel Football Association and asked it to draw the attention of Israeli authorities to the matter, FIFA said in a statement.

FIFA President Joseph Blatter expressed today grave concern and worry about the alleged illegal detention of Palestine football players, the statement said.

The reports FIFA received state that, in apparent violation of their integrity and human rights and without the apparent right of a trial, several Palestine football players have allegedly been illegally detained by Israeli authorities.

In particular, the mentioned reports refer to the Palestine player Mahmoud Sarsak, whose health is in a very delicate state due to the fact that he has been undergoing a hunger strike for approximately 90 days in protest of his alleged illegal detention.

FIFA said it had heard about the situation through correspondence with the Palestine Football Association, media reports and the world players' union FIFPro.

An Israel Football Association spokeswoman said Blatter's letter had been received and a response would be delivered to FIFA in the coming days.

FIFPro said that Sarsak, who lives in Rafah in the Gaza strip, was arrested at a checkpoint while on his way to the West Bank for a match with his national team in 2009.

He was interrogated for 30 days, imprisoned and denied visits from his friends or family, FIFPro said.

FIFPro said that his weight had dropped to 30 kgs following his hunger strike.

Sarsak's current term of detention term ends on Aug. 22 but there is no guarantee that it will not be renewed for a further six months, as it has been before, his family and lawyer said.

The lawyer, Mohammad Jabarin, said on Monday that Sarsak had broken his hunger strike and had begun to drink milk the night before.

In order to save his life, he agreed to start drinking milk and he will be drinking only milk...he was severely dehydrated but after he drank for the first time last night, he started doing a little better and is now in a stable condition, Jabarin told Reuters. (Additional reporting by Ori Lewis in Jerusalem and Jihan Abdalla in Ramallah; Writing by Brian Homewood in Poznan; Editing by John Mehaffey)