By Sara Sjolin, MarketWatch

LONDON (MarketWatch) -- European stock markets traded in tight ranges on Thursday, as investors were hesitant of making any major moves ahead of the highly anticipated European Central Bank meeting later in the day.

The Stoxx Europe 600 index was marginally higher at 343.65, but swung between small gains and losses.

The subtle moves came as most of Europe was waiting for the ECB to reveal its latest interest-rate decision. The bank is widely expected to cut interest rates and take the deposit rate into negative territory for the first time in euro-zone history, in an effort to spur growth and fight off worryingly low inflation. Most economists predict the central bank will also launch a package of liquidity measures to boost bank lending, which has been weak recently. Read: How to invest if the ECB cuts rates below 0%

The decision is out at 12:45 p.m. London time, or 7:45 a.m. Eastern Time, followed by a news conference with ECB President Mario Draghi at 1:30 p.m. London time.

Draghi -- the modern monetary Caesar

Economists at UBS called Draghi the "modern monetary Caesar" and said anything less than a 15 basis-point rate cut could disappoint the market. The main refinancing rate currently stands at a record low of 0.25%, and the deposit rate is at 0%.

"Draghi is dressing the move as deflation defiance," the UBS economists said in a note. "The move will not impact disinflation directly, of course -- but the reaction of the currency markets is very relevant."

The strong euro (EURUSD) has been cited as one of the reasons euro-zone inflation is stuck around a four-year low and monetary easing could weaken the currency. Since Draghi hinted at the ECB's May policy meeting at upcoming stimulus measures, the shared currency has been steadily declining from almost $1.40, to around $1.36. Ahead of the meeting on Thursday, the euro traded at $1.3617, a touch higher than recorded on late Wednesday.

Index moves

Europe's equity benchmarks were trading in tight ranges ahead of the rate call. Germany's DAX 30 index fell 0.1% to 9,918.93, while France's CAC 40 index rose 0.1% to 4,503.60. The U.K.'s FTSE 100 index dropped 0.3% to 6,800.22.

The Bank of England releases its monetary decision on Thursday as well, but is -- unlike the ECB -- widely expected to keep its key lending rate at a record low 0.50% and make no changes to its 375 billion-pound ($628 billion) asset-purchase program. The BOE decision is out at noon in London, or 7 a.m. Eastern Time.

Among movers in Europe, shares of Volvo AB lost 2.4% after UBS cut the truck maker to sell from neutral.

Shares of BHP Billiton PLC (BHP) dropped 0.7% after RBC Capital Markets shifted its preference within the mining space from BHP to Rio Tinto PLC (RIO).

In data releases on Thursday, Eurostat said euro-zone retail sales in volume terms rose 0.4% in April, compared with March. Year-on-year, retail sales improved 2.4%, marking the strongest annual growth rate in seven years.

Meanwhile, the Ukraine-Russia standoff remained in the spotlight, as Western leaders gathered in Brussels for the second day of the Group of 7 (G7) summit that kicked off on Wednesday. U.S. President Barack Obama and European leaders warned the Kremlin they will introduce tougher economic sanctions if Russia doesn't stop the violence in eastern Ukraine.

More must-reads from MarketWatch:

Could the euro face a short squeeze after the ECB?

A stock-market prediction that's 'kind of scary'

U.K.'s economy is still vulnerable: BOE official

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