Early reports indicate it was the work of US-ally Mahmoud Abbas’ al-Aqsa Martyrs’ Brigades.

GAZA CITY — A bomb attack on a Tel Aviv public bus Wednesday injured at least 21 people — three seriously — shattering the sense of security in Israel’s second-largest city and raising questions about the fate of cease-fire talks underway to end the violence in the Gaza Strip.

The noon-time attack took place on a bus on a busy downtown street. Early reports from witnesses said a man was seen running toward the bus, throwing a bag inside and running away.

Israel police launched a massive manhunt and raised security levels nationwide, fearing additional attacks might take place.

It was unclear whether the attack was related to the ongoing clashes between Israel and the Gaza-based Islamist group Hamas, but police suspected that it was a terrorist attack.

In Gaza, Palestinians cheered and celebrated on hearing the news, announced from mosque loudspeakers along with Koranic songs about victory.