At least 15 people have been killed and 160 wounded in an Israeli air strike that hit a market near Gaza City, Palestinian officials say.

The explosion hit a busy fruit and vegetable market in Shejaiya, east of Gaza City, where hundreds of Palestinians were shopping, a spokesman for the Gaza health ministry said.

The attack came during a four-hour truce called by the Israeli military.

Hamas, which controls Gaza, had rejected the truce as meaningless.

Correspondents say it was unclear whether anyone in Gaza was aware that the partial ceasefire had been called.

The Israeli military said it would last between 15:00 and 19:00.

However it had warned that the truce would only apply to areas where Israeli soldiers were not currently operating, and it told residents not to return to areas they had previously been asked to evacuate.

Hamas spokesman Sami Abu Zuhri had rejected the truce as meaningless.

"The lull which Israel announced is media exploitation and has no value because it excludes the volatile areas along the border, and we won't be able to get the wounded out from those areas," he said in a statement.

Sirens continued to sound in southern Israel after the ceasefire, to warn of militant rocket attacks, and Palestinian doctors said another Israeli air strike after the truce was announced had killed seven people in Khan Younis.