Three people were seriously wounded late this morning when an Arab suicide-terrorist blew himself up near Tel Aviv\'s old central bus station area. Some 20 others are listed in light or light-to-moderate condition. Witnesses on the pedestrian mall, a popular area for foreign workers, related that a man asked a passerby, \"Is this N\'vei Shaanan St.?\" He was told that it was, and seconds later there was a large blast. Police said that the terrorist was apparently carrying the explosive on his person; he did not ride in on a motorcycle, as had first been thought. The police had earlier declared a heavy terrorist alert on the entire Sharon area, slightly to the north of Tel Aviv.