A massive truck bombing Thursday at a police training center in western Libya killed at least 60 people and wounded around 200 more, officials said.
The bomb exploded as hundreds of recruits gathered at the facility in the town of Zliten.
There has been no claim of responsibility.
Later Thursday, a separate car bombing at a Ras Lanouf checkpoint, east of Sirte, left at least six people dead and 11 wounded. Ras Lanouf and the nearby oil port of Es Sider have come under attack from Islamic State militants this week.
The United States condemned the bombings. A State Department spokesman said the Zliten incident reportedly killed as many as 65 people.
On Twitter, Martin Kobler, the head of the United Nations Support Mission in Libya (UNSMIL), referred to the Zliten bombing as a "suicide attack."
"I condemn in the strongest terms today's deadly suicide attack in Zliten, call on all Libyans to urgently unite in fight against terrorism," he said.
Libya is split between the Islamist administration that seized Tripoli and the internationally-recognized parliament that fled east to Tobruk.
Members of Libya's rival governments last month signed a peace deal, despite concerns about the legitimacy of the much-disputed pact.
The country has been in chaos and political uncertainty since dictator Moammar Gadhafi was overthrown and killed in 2011.