Oil prices started the week higher on Monday as global stock markets soared on growing expectations that the U.K. is likely to remain in the European Union after this week’s referendum.

Brent crude, the global oil benchmark, flirted with the key $50 (£34.13) a barrel mark, rising 1.6% on London’s ICE Futures exchange. On the New York Mercantile Exchange, West Texas Intermediate futures were trading up 1.6% at $48.75 (£33.27) a barrel.

Opinion polls published over the weekend suggest that the U.K. was more likely to vote to remain in the EU in Thursday’s referendum. A poll by Survation published in the Mail on Sunday newspaper showed 45% backing for remaining in the EU and 42% in favour of leaving. A poll-of-polls, averaging the past six polls in the U.K. vote, has returned to 50/50, while the bookmakers’ odds for Brexit fell sharply from last week.

The Stoxx Europe 600 jumped 3.4%, extending Friday’s momentum, while the British pound surged 2.1% against the dollar. That followed gains in Japan and Hong Kong.