LONDON—Oil prices fell around $7 a barrel on Monday as investors pinned hopes on diplomatic efforts between Ukraine and Russia to end their conflict, while a surge in COVID-19 cases in China spooked the markets. Brent was down by $6.78, or 6 percent, at $105.89 a barrel at 1358 GMT and U.S. crude fell $7.01, or 6.4 percent, to $102.32. Both benchmarks have surged since Russia’s Feb. 24 invasion of Ukraine and are up roughly 40 percent in the year to date. Ukrainian and Russian negotiators began to talk again on Monday. Negotiators had given their most upbeat assessments after weekend negotiations, suggesting there could be positive results within days. “Beside new talks between Ukraine and Russia, I guess new lockdowns in China are the reason for a negative start of the week for crude oil,” said UBS analyst Giovanni Staunovo. A northeastern Chinese province on Monday imposed a rare …