UPDATE 1-US online holiday spend up 3 pct -comScore

* U.S. online holiday spending reaches $16 bln, up 3 pct

* Online sales slowed after Cyber Monday

SAN FRANCISCO Dec 8 (Reuters) - U.S. online holiday spending has risen 3 percent this holiday season, but shopping online slowed over the weekend after the special deals and discounts offered by retailers on Cyber Monday ended, analytics firm comScore Inc (SCOR.O) said on Tuesday.

For the first 36 days of the November-December holiday season, online holiday spending reached nearly $16 billion, comScore said, up 3 percent from a year ago. For the week ending Dec. 6, comScore said online holiday spending rose 3 percent to $4.6 billion.

Last week began with a bang, with online sales on Cyber Monday, which was Nov. 30, rising 5 percent to $887 million. But comScore said the week ended on a softer note, posting negative year-over-year growth rates during the weekend.

"We are anticipating heavy spending for the current week, making it an important determinant for how the holiday season as a whole will perform," said comScore Chairman Gian Fulgoni in a statement. "Hopefully, we'll see a return to the growth rates we observed during the earlier part of this past week and that the weekend softness was just a temporary hiccup."

Cyber Monday refers to the Monday after the U.S. Thanksgiving holiday when retailers, ranging from Wal-Mart Stores Inc (WMT.N) to Amazon.com Inc (AMZN.O) offer deep discounts or limited-time only deals on their websites to lure holiday shoppers. (Reporting by Nicole Maestri; editing by Gunna Dickson))