Hamas said it had suspended negotiations on the release of a captured Israeli soldier because the Jewish state was not respecting the terms of a truce with the group. "Hamas has suspended indirect negotiations with the enemy over (Corporal Gilad) Shalit because of the non-respect by the enemy of the terms of the truce, notably the opening of crossing points and authorising the entry of all merchandise into the Hamas-controlled Gaza Strip", said spokesman Osama al-Muzeini on Friday. Mr Muzeini was speaking as Israel again sealed off Gaza in retaliation for a rocket attack, itself a violation of the June 19 ceasefire between the two sides. The truce was supposed to lead to the easing of a crippling blockade Israel imposed after the Hamas seized power in Gaza more than a year ago, but the military said the crossings would stay closed until at least Sunday. Egypt has been mediating with the two sides over the eventual release of Mr Shalit, seized in a June 2006 cross-border raid by militants from Hamas and other Palestinian groups. A Hamas delegation had cancelled plans to travel to Egypt on Thursday for talks on the proposed prisoner exchange. Mr Muzeini added: "We apologised to our Egyptian brothers and explained to them that the enemy did not respect the terms of the truce and that we could therefore not trust them to respect a possible agreement on a prisoner exchange," he said. Negotiations would resume at a date to be set "once the enemy demonstrates it is serious and respects the agreements that have been reached." Mr Muzeini said Hamas wants 1,000 prisoners eventually be released, with 450 who are serving long sentences being freed in a first stage as part of any deal. To date Israel has approved the names of only 70 of the 450, he said. "I believe that if the enemy finds itself faced with a tough negotiator, it will end up making concessions," Mr Muzeini added. The negotiations have stalled primarily over Israel baulking at releasing people with "blood on their hands." The head of the Hamas government in Gaza, Ismail Haniya, said that the closing of the crossings "demonstrates that Israel is not seriously applying the ceasefire agreement reached under Egyptian mediation." *AFP