Hamas has responded to a Palestinian rocket attack on Israel by Fatah-linked militants today by saying it would "take the necessary measures" against other factions to ensure the ceasefire is held.
The Fatah-linked al-Aqsa Martyrs' Brigades claimed responsibility for launching two rockets towards northern Israel in the early afternoon. The home-made Qassam rockets landed in Sderot's industrial zone, causing no injuries or damage.
A statement from the militant group demanded that Israel halt its military operations in the West Bank.
"The rocket attack was in response to Israeli violations. Any calm deal must end Israeli attacks on our people in the West Bank too," said Abu Qusai, spokesman for al-Aqsa Martyrs Brigades.
In an unprecedented move, Hamas said it would "take the necessary measures" against other factions to ensure the ceasefire is held.
Abu Qusai rejected the Hamas threat. A spokesman for the Hamas government, Taher al-Nunu, was quoted describing Fatah's actions as "unpatriotic".
The truce, hammered out by Egypt over months of separate talks with Israel and Hamas, does not include the West Bank.
Previous truces have come apart quickly because Gaza militants claimed the right to retaliate for Israeli raids in the West Bank.
Israel's Prime Minister Ehud Olmert came under pressure following today's rocket attacks from a strong rival, Foreign Minister Tzipi Livni, to retaliate. Livni, Israel's chief negotiator with the Palestinians, said she urged him to order "an immediate military response to every violation".
The latest strike followed salvoes on Tuesday launched by Islamic Jihad in response to an Israeli army raid that killed one of the group's commanders in the occupied West Bank. Israel said the raid was aimed at foiling attacks on its citizens.
The rockets prompted Israel to keep Gaza crossings closed for a second consecutive day. Under the ceasefire, the flow of goods into the territory is meant to rise gradually.
The truce, which took effect last Thursday and is known locally as the "calm", does not cover the West Bank, but several militant groups had threatened to retaliate for any Israeli operations there.
Agencies