The Israeli ambassador, Tzvi Cohen, said two Uzbek workers were killed in the attack, the third bombing at the embassy this year. No Israelis were hurt, Mr Cohen said.
A spokeswoman for the US embassy in the Uzbek capital reported no confirmed injuries from the explosion that happened outside the US embassy compound.
A spokeswoman for the general prosecutor's office said there also was a blast at their building, but she had no information on casualties. The Interfax news agency reported there were deaths in the explosion, citing an unnamed source at the office.
Uzbekistan - a country of 26 million people, mainly Sunni Muslims - has been struggling with a rise in Islamist militancy.
Israeli army radio reported that a suicide bomber detonated a belt of explosives at the barrier outside the Israeli embassy. However, Mr Cohen said he did not know if the blast was down to an explosive device or a suicide bomber.
Mr Cohen said four Israeli diplomats were safe inside the embassy building. All other Israeli personnel and relatives were accounted for and told to stay at their homes, he said.
Uzbek security forces conducted searches in the area of the building while the diplomats stayed inside.
Mr Cohen said the embassy had been attacked in March and April and security had been expanded.
The blasts come as 15 suspects are standing trial for a wave of violence earlier this year that left at least 47 people dead. Those attacks included central Asia's first-ever suicide bombings.
The suspects have pleaded guilty to charges of terrorism, murder and religious extremism and could face the death penalty. Several of the suspects on trial have said that the US and Israeli embassies were intended targets in the wave of explosions that killed 33 alleged militants, 10 police and four bystanders in April and May, officials say.
