TEL AVIV, Israel (CNN) -- A security guard at a beachfront cafe blocked a suicide bomber from entering the establishment early Wednesday, but the bomber blew himself up at the cafe's door, the city's police chief said.

At least four people were killed, one of them probably the bomber, authorities said.

The terror attack, which occurred beside the U.S. Embassy compound, left as many as 40 wounded -- two of them in very critical condition, four in serious condition, four moderately hurt and 21 with light injuries -- ambulance service officials said.

The cafe, Mike's Place, is located in an area that includes several bars, cafes, and nightclubs along the Mediterranean coastline.

"Suddenly there was an orange flash and a loud bang, and I ducked and then it was covered in smoke, and everyone was screaming, and then we ran out," said Barry Gilbert, a musician performing at the cafe whose shirt and pants were bloodstained. "It was just very, very, very messy as we were trying to get out."

Gilbert said about 100 people were inside at the time of the explosion.[...]