(Updates with market rebounding)
DUBAI, Sept 29 (Reuters) - Saudi Arabia's stock market rebounded in afternoon trade on Thursday on the back of petrochemical stocks, which rallied in response to OPEC's production deal to restrain output and prop up oil prices.
The main Saudi index dropped as much as 1.0 percent in early trade, continuing a slide triggered by this week's announcement of austerity measures including cuts to civil service bonuses and allowances. In the previous two days, it had lost 7.1 percent.
But petrochemical firms, their profit margins closely tied to oil prices, began recovering on Thursday afternoon after Brent oil surged above $48 a barrel overnight because of the OPEC deal. The largest petrochemical producer, Saudi Basic Industries, gained 2.6 percent while the main index added 1.5 percent.
This encouraged buying-back of a range of stocks, with Alinma Bank climbing 3.2 percent.
News that the U.S. Congress overwhelmingly rejected President Barack Obama's veto of legislation allowing relatives of victims of the Sept. 11 attacks to sue Saudi Arabia was negative, but bankers said it would have little impact on the markets because the economic implications for Riyadh, if any, were not yet clear.
Dubai's stock index closed 0.6 percent higher with gainers outnumbering losers 17 to nine. Dubai Parks and Resorts , which is due to open its amusement parks next month, added 0.6 percent and Emaar Properties rose 1.4 percent.
In Qatar, the main index ended 0.3 percent lower as Qatar National Bank which had led advances in the first hour of trade, slipped 0.1 percent. (Reporting by Celine Aswad; Editing by Andrew Torchia)