By Richard Hubbard

LONDON (Reuters) - Concerns that probable military strikes by Western powers against Syria could cause upheaval in the Middle East pushed oil up by over $2 a barrel on Wednesday, sent world shares lower for a second day and extended a rout in emerging markets.

Washington and its allies appeared to be gearing up for a strike against President Bashar al-Assad's forces, blamed for last week's chemical weapons attacks, a move which could prompt retaliatory action and hit crude supply in the region.

Brent crude traded above $117 at a six-month high and the U.S. benchmark soared to its highest level in over two years.

A scramble for safety sent MSCI's world equity index <.miwd00000pus> to a seven week low led by a sharp selloff on Wall Street, while the safe-haven yen hit a two-week high against the dollar.

Emerging markets such as Syria's neighbor Turkey, pummeled by an expected reduction in U.S. stimulus measures, were also hit, with some flows providing support in western Europe.

"The market feels an attack on Syria is highly probable but what they're concerned about is the retaliation," said Mike Gallagher, managing director of IDEAglobal.

In the Middle East, Dubai's stock index (.DFMGI) tumbled 5.2 percent after already plunging 7.0 percent on Tuesday, leaving it at a six-week low. It is still up 49 percent this year.

"We could see a wider spillover into the region which could easily push oil prices up, at least temporarily, to $120 or $125 a barrel," Gallagher said.