Global oil prices fell further on Monday on concern about an escalation of the Ukraine crisis after the downing of a Malaysian airliner last week, analysts said.
Investors were also eyeing developments in the Middle East after Israel launched a ground offensive against Hamas militants in Gaza, fuelling worries about crude supplies from the oil-rich region.
Brent North Sea for delivery in September fell 30 cents to $106.94 a barrel in London midday deals.
New York's benchmark West Texas Intermediate for August reversed 18 cents to $102.95 per barrel from Friday's closing level.
"Investors ... remain engaged to the unfolding situation between Ukraine, Russia and the West, as well as the ongoing Israeli ground assault of Gaza," said Sucden analyst Kash Kamal.
Desmond Chua, an analyst with CMC Markets in Singapore, added that investors are awaiting further news on whether the shooting down of the plane over Ukraine's airspace last week was carried out by separatist rebels supported by Russia.
He said proof of involvement by the pro-Moscow separatists would likely trigger stronger US and European sanctions against President Vladimir Putin's government, threatening to widen the crisis.
Russia is the world's second-biggest crude producer, and there are concerns its standoff with the West over Ukraine could affect supplies. Ukraine is also a major conduit for Russian gas exports to Europe.
"If the Russians were found to have assisted the rebels by providing the weaponry, the situation may escalate," Chua said.
All 298 people on board MH17 were killed after it was apparently blown out of the sky by a missile which the US said was fired from a system Russia provided to the separatists.
Tensions in the Middle East are also expected to put keep oil prices high.
Washington and the United Nations demanded an "immediate ceasefire" in Gaza early Monday as Israel pressed an assault on the enclave, pushing the Palestinian death toll to 509.
At an urgent meeting on Gaza, the UN Security Council urged an "immediate cessation of hostilities" in a call echoed by US President Barack Obama in a telephone conversation with Israeli Prime Minister Benjamin Netanyahu.