By Chao Deng 

Stocks rallied across most of Asia Friday, after the European Central Bank unveiled a bond-buying program aimed at shoring up the flagging eurozone economy.

Australia's S&P/ASX 200 finished up 1.5% at 5501.80 and Hong Kong's Hang Seng Index up 1.3% at 24849.68 with investors expecting that Europe's bond-buying efforts will support money flows to riskier investments, including stocks.

The ECB's move was widely expected, although the size of the asset-purchase plan was larger than many had forecast--the bank said it would buy 60 billion euros a month in assets including government bonds, debt securities issued by European institutions and private-sector bonds. Underscoring how quickly the move is likely to encourage easing across the region, Denmark's central bank cut its main interest rate overnight.

The Shanghai Composite capped a volatile week. It ended up 0.3% to 3351.76 Friday. HSBC's China flash manufacturing PMI report for January rose to 49.8 from 49.6 in December, which despite showing a slight strengthening indicates continued economic deceleration amid a slowing property sector. A reading above 50 indicates expansion, while a reading below 50 indicates contraction.

The benchmark lost 0.7% for the week, however, after investors had taken profit on concerns that tighter rules toward Chinese brokerages would spell an end to a multi-month rally. Shanghai shares plunged 7.7% Monday after a sudden move by Chinese regulators to curb borrowing.

Still, China's central bank has also pumped more liquidity into the financial system in recent weeks, spurring hopes of further easing of monetary policy that will bring gains to the stock market.

The yuan fell as low as 6.2237 against the U.S. dollar, after China's central bank pushed down the rate Friday by the most since last March. Its weaker guidance comes as central banks across the world push their currencies lower through aggressive monetary easing policies.

The ECB's move sent the euro to new 15-month lows against the Japanese yen during Asia trade.

In Hong Kong, shares of Hutchison Whampoa Ltd. jumped 3% after the company said it has agreed to enter into exclusive talks to buy U.K. mobile-phone operator O2 for potentially more than GBP10 billion ($15 billion). A deal would be the latest large consolidation move in Britain's fast-changing wireless market.

In Australia, utilities and energy stocks led gains after a jump in crude-oil prices. Woodside Petroleum Ltd. was up 1.8%, while Origin Energy Ltd was up 2.5%.

Oil prices on the New York Mercantile Exchange were up 1.6% at $47.05 after news that Saudi Arabia's King Abdullah bin Abdulaziz al Saud died--raising questions about how a leadership transition in the world's largest oil exporter could affect its production policy and that of the Organization of the Petroleum Exporting Countries, according to analysts.

Anjani Trivedi and Mia Lamar contributed to this article.

Write to Chao Deng at Chao.Deng@wsj.com

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