Palestinian gunmen opened fire in the midst of a long group of people waiting to cross from the Gaza Strip into Egypt on Friday and tossed a grenade at Palestinian officials, wounding two of them.

Palestinian sources said the militants were trying to clear the way for their relatives to get closer to the border.

However, the violence - which wounded two Palestinian officers - ended up causing European monitors to close the border briefly. The crossing was reopened by early afternoon, after Palestinian officers took control of the crowds.

The shooting began shortly after the Rafah crossing opened for the first time in about a month.

Thousands of people were pushing and shoving as they waited to cross the border Friday. The gunmen fired in the air and threatened people at gunpoint so their relatives could move closer to the border.

The Rafah crossing was expected to be open for two days, to allow thousands of Palestinians to pass through en route to Saudi Arabia, to celebrate the Muslim holy month of Ramadan, said Jabbour.

The crossing is the Gaza Strip's main gateway to the world, and has endured frequent closures since the June 25 capture of Israeli soldier Gilad Shalit by Hamas-linked militants. The last time the border opened was August 25.

By mid-morning Friday, only one bus carrying some 50 Palestinians had crossed the border, said Hani Jabbour, a Palestinian diplomat stationed at the border terminal.

Some 1,500 Palestinians stranded in Egypt were also waiting to return home to Gaza, Jabbour said.

The Egypt-Gaza border is controlled by the Palestinian Authority and Egypt, with the help of European Union monitors. Israel demanded its closure after Shalit's capture, to prevent him from being smuggled out of Gaza.