At least 10 people were injured on Wednesday in an explosion on a bus in central Tel Aviv, Israel's emergency services said, with police saying the source of the blast was not immediately clear.

"There are about 10 people wounded of whom three are in serious condition," emergency services spokesman Zaki Heller told public radio.

"There was an apparent explosion on a bus in Shaul HaMelech Street in Tel Aviv. The background and circumstances are not clear yet," police spokeswoman Luba Samri told AFP.