By Rebecca Harrison

JERUSALEM, April 1 (Reuters) - Israel has turned away more sick Palestinians from Gaza seeking treatment since Hamas seized control of the enclave and several have died each month unnecessarily, a U.N. agency said on Tuesday.

The World Health Organisation (WHO) said Israel denied entry permits to 18.5 percent of patients seeking to leave the Gaza Strip in 2007 versus 10 percent in 2006.

In December 2007, 36 percent were denied permits compared with 8.5 percent in December 2006.

The WHO said the number of applicants and the percentage of those turned away surged after Hamas Islamists seized control of Gaza in June, the crossing to Egypt was closed and Israel tightened restrictions on the enclave.

Israel could not provide figures for how many sick Gazans were granted travel permits last year. A senior defence official denied the system caused unnecessary death, but said Israel was wary of would-be suicide bombers using illness as a cover.

Israel says its blockade on the enclave is a response to cross-border rocket fire by militants while international organisations have condemned it as collective punishment.

"Even under fire and under threat we still coordinate the health needs of Gaza's population," said Colonel Nir Press, head of Israel's Coordination and Liaison Administration for Gaza.

Shortages of medicine, equipment and trained medics, which local officials blame on Israeli restrictions, mean advanced health care is virtually non-existent in the Gaza Strip.

Thousands of Gazans have been treated over the years in the Jewish state.

The WHO said 32 Gazans died between Oct. 1 and March 2 whilst waiting for travel permits.

It could not provide comparative figures and said it was hard to measure whether faster treatment would have saved them, characterising many of the deaths as unnecessary.

"All these tragedies could have been easily avoided," WHO's head of office for the West Bank and Gaza, Ambrogio Manenti, told a news conference. Palestinian medical officials in Gaza say more than 100 Gaza patients have died since June after being denied permits.

Israel pulled troops and settlers out of the Gaza Strip in 2005 but effectively still controls its borders. Palestinians say that means Israel must observe Geneva Convention obligations as an occupying power to provide services for the territory.

Egypt has allowed some Gazans in for treatment, but has agreed with Israel to keep its border largely closed. (Editing by Diana Abdallah)

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