LUANDA, Oct 21 (Reuters) - Angola's foreign exchange reserves rose for a third consecutive month in September to $12.8 billion from $12.6 billion in August on higher oil prices and exports, a central bank document showed on Wednesday.

Angola, which rivals Nigeria as Africa's biggest oil producer, is recovering from a sharp drop in oil revenue this year that prompted the government to cut back on public spending, devalue the national currency and delay payments of up to $2 billion to building firms.

Banco Nacional de Angola's foreign reserves are down almost 30 percent this year.

However, analysts expect these holdings to continue to rise on the back of firm oil prices.

(Reporting by Henrique Almeida, editing by Mike Peacock) (For more Reuters Africa coverage and to have your say on the top issues, visit: http://af.reuters.com) Keywords: ANGOLA RESERVES/

(Reuters messaging: henrique.almeida.reuters.com@reuters.net; email: henrique.almeida@reuters.com; tel 244 912 304 020)

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