Japanese shares fell sharply on Thursday as worries continued over the Greek debt crisis and whether problems would hit other European countries.

受希腊债务危机影响，以及此次危机是否会影响到其他欧洲国家经济的担忧，日本周四股价暴跌。

The Nikkei index（日经指数） fell 3.3% after it reopened following a three-day holiday.

The European Central Bank (ECB) meets later amid growing concerns over the economies of Greece and Portugal.

The bank is under pressure to signal how it plans to shore up（支持，加固） the euro, which hit a fresh 13-month low against the dollar in Asian trading.

"The focus stays on the euro as the contagion（蔓延，传染病） trade persists," said analysts at JP Morgan.

They added that Thursday's ECB meeting had "grown immensely in importance as the redeployment of some form of credit crisis tools seems increasingly possible".

The ECB is expected to keep interest rates on hold at 1%.

However, markets will be closely watching comments from the bank for hints that it is planning to start a new round of buying up（尽量收购，全买） government debt.

Peter Westaway, European chief economist at Nomura International, agreed that the ECB faced a "really important meeting".

"This crisis is not just about Greece. it's about the integrity（正直，诚实） of the euro as a whole," he told the BBC.

Debt repayments

Japan's Nikkei 225 stock average fell 3.3% to 10,698.87 on Wednesday with Hong Kong's Hang Seng index（恒生指数） also sliding.

The euro was trading at $1.2821, down from $1.2823 late on Wednesday.

Fears Greece's debt crisis could spread to other countries intensified on Wednesday when ratings agency Fitch said it was considering a downgrade of Portugal's government debt.

Fellow ratings agency Moody's Investor Services said it would be reviewing Portugal's bond rating, which could lead to a possible downgrade.

There are fears that Portugal, like Greece, may also have trouble repaying debt and that they may have to call on eurozone loans.

Meanwhile, Greek authorities are braced for more violent protests over plans for austerity measures（紧缩措施） in Greece which are seen by eurozone members as a crucial condition of the bail-out.

Three people were killed in Athens on Wednesday when protesters set fire to a bank during a general strike over the planned measures.