Israel says it has closed its border crossings with Gaza in response to a Palestinian rocket attack on southern Israel that breached a ceasefire.

Israel said the attack was a "grave violation" of a truce in Gaza between Israel and the militant group Hamas.

Israel had been allowing more imports into Gaza since the truce was agreed, but officials said the crossings would now remain closed until further notice.

Hamas, which controls Gaza, said the closings violated the truce agreement.

The Erez pedestrian crossing remains open to diplomats and journalists.

Blockade

Hamas leader Khalil al-Haya said the group remained committed to the six-day-old ceasefire with Israel and it had called on all Palestinian groups to respect it.

However, he said that Hamas would not act as Israel's "police force" in confronting militants who breached the truce.

The rocket attack on Sderot on Tuesday was carried out by Islamic Jihad, which said it was to avenge an Israeli raid in the West Bank, in which two died.

No injuries were reported in the attack, the first on Israel since the truce agreement came into force.

The Israeli government had previously warned it would respond with considerable force if any of the Palestinian groups resumed violence.

Speaking at a donors' conference in Berlin on Tuesday, Palestinian Prime Minister Salam Fayyad said it was "essential for the ceasefire to be sustained".

"Whatever damage has been done to the process, that damage should be undone as quickly as possible," he said.

The Egyptian-brokered truce between Israel and Hamas in Gaza started on 19 June and is supposed to last six months.

It is designed to halt Israeli incursions into the Gaza Strip, and to stop missiles being fired from Gaza into southern Israel.

Israel pledged to ease its blockade on Gaza, and there may be further talks on a prisoner exchange.