GAZA, June 9 (Reuters) - Arab League chief Amr Moussa plans to visit the Gaza Strip on Sunday in what the ruling Hamas movement called a sign of mounting Arab pressure for an end to an Israeli blockade of the Palestinian territory.

The visit will be the first by a secretary-general of the Arab League to the Gaza Strip and come nearly two weeks after Israeli marines raided an aid flotilla, drawing violent resistance and killing nine pro-Palestinian activists.

An aide said on Thursday that Moussa would enter the enclave on Sunday, for a one-day visit, from Egypt via the Rafah crossing that Cairo opened after the May 31 Israeli interception of the Turkish-flagged Mavi Marmara ship.

Egypt had largely kept Rafah closed, bolstering an Israeli blockade of the Gaza Strip, after Hamas seized the territory in a brief civil war in 2007 with Fatah movement fighters loyal to Western-backed Palestinian President Mahmoud Abbas.

Hamas spokesman Sami Abu Zuhri said Moussa's visit reflected a growing sense among Arabs that the Gaza blockade must end.

Arab League officials in Cairo said the trip also was aimed at giving momentum to reconciliation talks between Hamas and Fatah that Egypt has sponsored but which have failed to bridge deep mistrust between the two rivals.