GAZA, May 11 (Reuters) - Egypt opened its border with Gaza for the first time in three months on Wednesday, giving Palestinians a two-day respite from a closure stemming from friction between Cairo and the enclave's Islamist rulers.

Egypt's shuttering of Rafah and destruction of cross-border smuggling tunnels, along with tight restrictions imposed by Israel along its own frontier with Gaza, have deepened economic misery for many of the 1.9 million Palestinians in the enclave.

Egypt's military-backed government has kept its border with the Gaza Strip largely closed since Mohamed Mursi of the Muslim Brotherhood was ousted as president three years ago.

Egyptian officials view Gaza's governing Hamas group as a threat, accusing it of supporting an Islamist insurgency in the Sinai peninsula bordering the Palestinian territory. Hamas denies the allegation.

Some 30,000 Gazans are on a waiting list to cross at Rafah. Only a few thousand, including patients, students and holders of residency permits in third countries, were likely to do so on Wednesday and Thursday before it closes again.

"I have been waiting for several months to get a chance to have advanced cancer checks in Cairo," said Umm Ahmed, a 55-year-old Gaza resident, urging Egypt's president to reopen the Rafah crossing for good because "we are brothers, not enemies."

For Gazans who live or work outside the enclave, a visit home is hard to schedule, and it carries the risk of being stuck in the territory and losing residency rights in host countries.

"You never know when the crossing will be open, so if you want to come and visit your family at home, you should be prepared to risk your job," said a Gaza merchant who does business in the Gulf.

The Palestinian Embassy in Cairo said Rafah was opened at the request of West Bank-based Palestinian President Mahmoud Abbas, who met Egyptian leader Abdel Fattah al-Sisi this week.

Hamas ousted Abbas's Fatah movement from power in Gaza in a brief civil war in 2007.

At Cairo International Airport, immigration sources said 90 Palestinians from Gaza, stranded in third countries, had arrived and would travel by bus to Rafah. The sources said another 120 Palestinians were expected to land later.

Last week, Israel said it planned to reopen a second border point for commercial traffic into Gaza, a step toward gradually easing the blockade it imposed since 2007.

Israel says its blockade prevents the movement of militants and stops construction materials that could be used by Hamas to make bunkers and tunnels. Palestinians there say they are under siege and are unable to rebuild homes destroyed by Israeli bombing in a 2014 war.

(Additional reporting by Abdel Nasser Abul Fadl in Cairo; Writing by Nidal al-Mughrabi; Editing by Jeffrey Heller/Mark Heinrich)