UPDATE 1-Saudi Arabia's Southern Cement Q3 net down 5.4 pct

* Third-quarter profit slips 5.4 percent

* Exports ban continues to dampen earnings

* Shares underperform main index

(Adds details, background)

RIYADH, Oct 20 (Reuters) - Saudi Arabia's Southern Province Cement Co (SPCC) 3050.SE, the kingdom's largest cement maker by market value, posted a 5.4 percent fall in third-quarter net profit due to a long-standing exports ban.

Quarterly earnings amounted to 141 million riyals ($37.60 million) compared with 149 million riyals in the same period a year ago, the firm said in a statement on the bourse website on Tuesday.

Operational profit declined by 5.2 percent to 146 million riyals from 154 million riyals in the year-earlier period.

"The decline in net profit is due to the continuation of the export ban on cement and clinker," the firm said, adding that demand had also fallen during Islam's holy lunar month of Ramadan, which ended on Sept. 19.

Shares dipped 0.74 percent to 67.5 riyals while the main Tadawul index .TASI was at 6,550, up 0.24 percent.

The firm reviewed expansion plans in June due to the export ban. [ID:nL2706737]

Other cement makers also posted declines in profits this quarter due to an export ban imposed since June 2008.

The government had banned cement exports to force prices down after large infrastructure projects sent demand soaring at a time cement firms eyed more lucrative markets abroad.

The ban coincided with capacity expansions that saturated the local market pushing prices and profits of many firms down.

On Monday, Saudi Arabian Cement Co 3030.SE posted a 14.9 percent drop in net profits to 123 million riyals.

This was below the average of 184 million riyals two analysts surveyed by Reuters had expected. [ID:nL4414167] ($1=3.750 riyals) (Reporting by Asma Alsharif, Editing by Inal Ersan and Mike Nesbit)