Israel closed its border crossing with the Gaza Strip on Wednesday as doubts intensified over a rocket fired by the Palestinian Islamist group Hamas, breaching a week-old ceasefire agreement.

Israeli military officials said the closure was a response to the firing of four rockets from Gaza into southern Israel yesterday. Israel said the attack was a grave violation of the peace agreement in Gaza between Israel and the militant group Hamas.

The rockets left two people mildly injured and was said to be in response to the killing of one of Hamas' commanders in the occupied West Bank earlier in the day.

Israel was expected to open the border crossing at 8 a.m. local time to let imports to reach the impoverished territory. But Israeli military liaison official Peter Lerner said they would stay closed until further notice.

Any reopening [of the crossings] will be in accordance with security considerations, he told Reuters.

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

Under the ceasefire, Israel and the Palestinian militant groups were expected to halt violence in the Gaza Strip and Israel was to ease its tough economic blockade of the territory.