The dollar opened the month on a strong footing on Monday, recording gains against the euro and other major counterparts as forex investors paid close attention to an independence vote in Spain's Catalonia.

The dollar index, which gauges the strength of the greenback against six major of its major rivals, added 0.1 percent to 93.192. Liquidity was expected to be thin on Monday, with China, South Korea, Hong Kong and India markets closed for public holidays.

EUR/USD slipped more than half a percentage point to 1.1734, as traders nervously monitored the unfolding situation in Spain. Army police used batons and rubber bullets to disrupt the Catalan vote on Sunday in a show of force that left hundreds injured.

Catalonia's regional leader said the door to a unilateral declaration of independence from Spain was open as voters defied a violent police crackdown and, according to regional officials, voted 90 percent in favor of breaking away.

USD/JPY rose above 113 to 113.05 as the Bank of Japan Tankan Manufacturing Index showed business mood was more elevated than expected. Today’s data showed a figure of 22 versus expected 18, bringing confidence to the highest in a decade. Market analysts cited “a weak yen and a stronger global economy to have fueled record profits in Japan, despite trade tensions and North Korea’s nuclear program creating tension.”