GAZA, Sept 21 (Reuters/Nidal al-Mughrabi) - Hamas said on Tuesday that Egypt has detained one of its senior officials and Egyptian media reported he was being questioned over the death of an Egyptian soldier and a communications equipment shipment.

The Sept. 13 arrest of Mohammed Dababesh worsened already poor relations between Egypt and the Palestinian Islamist group, which has refused to sign a document drafted by Cairo on reconciliation between Hamas and the rival Fatah movement.

We see this as an offence to Palestinian-Egyptian relations. It was unacceptable and unjustified, Hamas spokesman Fawzi Barhoum told a news conference in the Hamas-run Gaza Strip.

Dababesh, who was detained at Cairo airport after flying in from Saudi Arabia, is a senior official in Hamas's internal security service.

Newspapers in Cairo that reported on Dababesh's arrest quoted Egyptian security sources as saying he was being interrogated over a large shipment of two-way radio sets, seized by Egypt, that had been destined for Hamas forces in Gaza.

The Egyptian media reports also said that interrogators were seeking information from Dababesh on the killing of an Egyptian soldier last year during an exchange of fire on the border between Palestinian gunmen and Egyptian forces.

Commenting on the reports, Barhoum said: Dababesh was never a danger to Egyptian security. He noted that Dababesh had taken part in Egyptian-hosted Palestinian reconciliation over the past three years.

Egypt has largely sealed its border with the Gaza Strip since Hamas, which opposes Western-backed President Mahmoud Abbas's peace efforts with Israel, seized the coastal enclave from forces loyal to his Fatah group in fighting in 2007. A network of smuggling tunnels runs underneath the Egyptian-Gaza frontier. Egypt reopened its Rafah crossing with the Gaza Strip in June in both directions, allowing certain categories of passengers to pass.