Former Israeli prime minister Ehud Olmert was sentenced today to eight months in jail for accepting illegal payments from a US businessman, having previously been given a six-year term in a separate corruption case.

Olmert's lawyers said they would appeal to the Supreme Court against the new conviction and prison term.

Today's sentence stemmed from a verdict in March that found that Olmert, while serving as industry and trade minister from 2003 to 2005, accepted cash-filled envelopes from an American businessman who hoped to further his interests in Israel.

The court convicted him of fraud and breach of trust on the basis of new testimony from a former aide who had accepted a plea bargain.

Last May, Olmert was sentenced to six years in jail for accepting $160,000 in bribes linked to a real estate deal in Jerusalem while serving as the city's mayor.

Olmert, 69, is currently appealing that conviction in the Supreme Court, having denied wrongdoing in both cases.

He remains at liberty while the appeals process runs its course. A Supreme Court decision on the first appeal is expected in the next couple of months, his lawyers said.

Olmert became prime minister in 2006 but announced his resignation in 2008 after the corruption allegations surfaced, cutting short his pursuit of a peace deal with the Palestinians.

He stayed on until a new government took office following national elections in 2009.