The US intelligence whistleblower Edward Snowden has urged Israelis to be on guard against both government and private surveillance.

In a speech by video link from his exile in Moscow to an invited audience in Tel Aviv, the 35-year-old warned that accepting too much government surveillance and too easily acceding to the argument that it is needed for security reasons posed serious risks.

The former US spy agency contractor also spoke of the NSO Group, the Israel-based company known for its Pegasus spyware, which independent experts have said is used in a number of countries with poor human rights records.

In one case, international experts investigating the disappearance of 43 students in Mexico in 2014 were targeted with the spyware after it had been sold to the government, the experts said.  

NSO Group says its product is intended to be used only for investigating and preventing crime and terrorism.

The United States has charged Snowden with espionage and theft of state secrets, following his massive leak of classified documents in 2013.

He leaked thousands of classified documents to the press, which revealed the vast scope of surveillance of private data put in place after the 9/11 attacks.

The former US spy agency contractor said he still loves his country and hopes to return home.