(Reuters) - Home and auto insurer Allstate Corp , considered to be one of the companies most exposed to insured losses from superstorm Sandy, said it expects October catastrophe losses to exceed $150 million though a full estimate cannot be made at this time.

Allstate, one of the biggest insurers in the northeastern United States, said on October 31 the storm would not materially affect its overall financial condition.

Sandy appears to have caused twice or even three times the losses of last year's Hurricane Irene, but final estimates will be hard to come by for some time because of the scale of the disaster, catastrophe forecasting companies have said.

Disaster modeling company RMS expects U.S. insured losses of $20 billion to $25 billion.

Property insurer Chubb Corp , a major player in the U.S. Northeast, suspended share buyback last week because it could not yet estimate Sandy's impact.

Shares of Allstate, which have risen 38 percent this year, were almost flat at $38.46 on the New York Stock Exchange on Thursday. (Reporting by Tanya Agrawal in Bangalore)