TORONTO -- North American stock markets were well off session highs mid-morning Thursday amid rising tensions between Russia and Ukraine.

Toronto's S&P/TSX composite index benefitted from another heavy and generally positive slate of earnings news. The index was up 13.25 points to 14,546.64 after Russia's defence minister announced new military exercises in Russia's south and west in reaction to mounting unrest in eastern Ukraine and NATO exercises in Poland. That development came just hours after Ukrainian troops killed at least two pro-Russia insurgents in eastern Ukraine, leading Russian president Vladimir Putin to threaten Kiev with unspecified consequences.

The Canadian dollar also pared early gains but was still ahead 0.02 of a cent to 90.67 cents US.

New York's Dow industrials was down 11.97 points to 16,489.68 despite well-received earnings reports from General Motors and Caterpillar.

The Nasdaq gained 4.54 points to 4,131.51 as Facebook and Apple blew past expectations while the S&P 500 index added 0.57 of a point to 1,875.96.

In Canada, Potash Corporation of Saskatchewan Inc. (TSX:POT) posted quarterly net income of US$340 million or 40 cents a share, compared to 63 cents per share, or US$556 million, in the same period last year. The company's guidance was for between 30 and 35 cents per share and its shares gained 18 cents to $38.53.

General Motors says first-quarter profit fell 86 per cent to $125 million or six cents a share as a series of recalls dragged down its earnings. Excluding one-time items, GM made 29 cents per share, far above analyst estimates of three cents per share and GM shares were up 90 cents to US$35.29.

Caterpillar's first-quarter earnings climbed five per cent to $922 million, or $1.44 per share. Earnings totaled $1.61 per share, excluding restructuring costs. Total revenue was nearly flat at $13.24 billion. Analysts forecast earnings of $1.21 per share on $13.09 billion in revenue. Caterpillar shares are up $2.62 to $106.

After the close Wednesday, Facebook posted earnings ex-items of 34 cents a share versus the 24 cents that analysts expected. Revenue of $2.5 billion beat estimates of $2.36. The stock was well off session highs, up just a dime to $61.46.

Shares in Apple Inc. jumped $39.80 or 7.58 per cent to $564.55 after the company announced Wednesday that it was increasing its dividend by eight per cent to $3.29 per share and that it will buy back an additional US$30 billion of its stock. Quarterly earnings rose seven per cent to $10.2 billion, or $11.62 per share, while revenue climbed by five per cent to $45.6 billion. The company also will execute a seven-for-one stock split in early June.

Commodity prices were mixed as May copper ran up five cents to US$3.11 a pound and the base metals sector edged up 0.1 per cent.

Escalating tensions between Russia and Ukraine pushed June crude in New York up 63 cents to US$102.07 a barrel. The energy sector dropped 0.3 per cent.

The gold sector was the leading decliner, down 0.5 per cent even as June bullion shed early losses to move up $7.60 to US$1,292.20 an ounce.

The Globe and Mail reported that Barrick Gold Corp. (TSX:ABX) has formally asked Newmont Mining Corp. to resume merger talks after their negotiations hit an impasse late last week. Other sources have said the North American-based gold miners had come close to agreeing on an all-stock deal, but their discussions broke down over which assets to spin out from the combined company.

Gerry McCaughey plans to step down as president and CEO of CIBC (TSX:CM) effective April 30, 2016. The announcement came just ahead of the bank's annual meeting.