At least 18 people were injured when an explosion hit a bus in central Tel Aviv on Wednesday, Israeli police said, accoridng to RIA Novosti.

A spokesperson for the Islamist group Hamas said it welcomed the bombing as a "natural response" to the ongoing Israeli bombardment of Gaza, but said it was not behind the attack. In Israel, politicians including Deputy Parlimentary Speaker said the bombing meant Israel had no choice but to invade Gaza.

Police in Tel Aviv said they were seeking a suspected bomber and that one of the injured is in a “serious” condition.

Around 140 Palestinians have been killed in Israel's eight-day air and naval attack on Hamas-ruled Gaza, officials say. Gaza’s health ministry says many children are among the Palestinian dead.

Israel says it began its attack on the city of 1.7 million in response to a surge in rocket attacks from Gaza.

Palestinian rockets continued to hurtle toward Israeli towns and cities on Wednesday, November 21 but most were knocked down by the sophisticated Iron Dome air defense system. Israel says five people have been killed by Palestinian rockets in the last eight days.

A spokesman for Israeli Prime Minister Benjamin Netanyahu tweeted that a second bomb that did not explode had also been found on the bus in Tel Aviv.

An Israeli Defense Forces spokesman said on Twitter that Hamas members had celebrated on the streets of Gaza as news of the bus bombing broke.

The bombing comes amid frantic negotiations to end the violence.

Israel’s last invasion of Gaza, in 2008-2009, killed 1,400 Palestinians, the majority of them civilians. Thirteen Israelis died in the 22-day-long Operation Cast Lead.

A Haaretz-Dialog poll taken on Sunday indicated that 84% of the Israeli public supports the military campaign, with 12% opposing it. But only 30% would support a ground offensive in Gaza, the pollster reported.