TORONTO -- The Toronto stock market was lower Friday as nervous investors backed off going into the weekend amid rising tensions in Ukraine.

The S&P/TSX composite index dropped 80.77 points to 14,573.48 amid another slate of corporate earnings. The Canadian dollar was unchanged at 90.68 cents US.

U.S. indexes also retreated as the Dow Jones industrials tumbled 157.24 points to 16,344.41, the Nasdaq dropped 72.7 points to 4,075.64 and the S&P 500 index slid 16.97 points to 1,861.64.

There were scattered reports of violence as Ukrainian forces tried to end an occupation of government buildings by pro-Russian militia in more than 10 cities in eastern parts of the country. In turn, Russia's foreign minister has accused the West of plotting to control Ukraine and also announced military exercises near Ukraine's border.

"We can't dismiss what is going on there, it is a concern, it could escalate," said Gareth Watson, vice-president investment management and research at Richardson GMP Ltd.

At the same time, the economic cost to Russia for its stance toward Ukraine increased as Standard & Poor's cut Russia's credit rating to from BBB to BBB-minus -- one step above non-investment grade.

S&P said it took the step because the tense situation "could see additional significant outflows of capital from the Russian economy."

The latest round of tensions came at the end of what had been a generally positive week thanks to a series of better than expected corporate earnings in Canada and the U.S.

"What's more important is that we haven't seen any massive downgrades to guidance," added Watson.

"There's been a few tweaks to guidance going forward but not massive."

On Friday, automaker Ford said first-quarter net income fell 39 per cent to US$989 million, or 24 cents per share, down from $1.64 billion, or 41 cents per share, a year ago and seven cents below estimates. Revenue rose slightly to $35.9 billion, beating analysts' expectations for $34.2 billion and its shares fell 3.31 per cent to $15.78.

Shares of Microsoft ticked one cent higher to $39.87 after it reported after the close of markets Thursday quarterly earnings per share of 68 cents, five cents better than estimates. Revenue of $20.4 billion narrowly beat expectations of $20.39 billion.

In Canada, business software provider Open Text Corp. (TSX:OTC) posted quarterly net earnings of $45.8 million or 33 cents per share, up from $25.8 million or 22 cents in the comparable year-earlier period as revenue rose to $442.8 million from $337.7 million. The company also upped its quarterly dividend by 15 per cent to 17.25 cents a share. Its shares climbed $3.27 or 6.44 per cent to $54.08.

In other corporate developments, Canadian Oil Sands Ltd. (TSX:COS) lowered its production guidance during 2014 for the Syncrude Canada oilsands mine north of Fort McMurray, Alta., to between 95 million and 105 million barrels, compared with an previous estimate of 95 million to 110 million barrels as a result of a breakdown at one of its cokers, which help convert heavy oilsands bitumen into a lighter type of crude. Its shares fell $1.30 to $22.83.

The energy sector led decliners, down almost one per cent while June crude in New York gave back $1.09 to US$100.85.

May copper was unchanged at US$3.12 a pound and the base metals group was off 0.16 per cent.

The gold sector was the leading advancer, up 1.1 per cent as geopolitical worries drove June bullion up $11.50 to US$1,302.10 an ounce.