ICC Prosecutor Fatou Bensouda told the UN Security Council that pursuing accountability in the years since a 2011 rebellion toppled Moammar Gadhafi's regime has been increasingly difficult.
The North African country has split into two governments, one elected and the other backed by Islamists, and security has fallen apart amid militia violence.
The international court in June 2011 charged Gadhafi's son, Seif al-Islam Gadhafi, with murder and persecution linked to the violent suppression of the 2011 rebellion.
Libya has argued that its courts should be given precedence, because the ICC is a court of last resort that takes cases only when countries are unable or unwilling to pursue them.
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But appeals judges with the ICC earlier this year ruled that the Libyan charges were significantly different to those levied at The Hague.
The ICC also indicted Gadhafi's former intelligence chief, Abdullah al-Senoussi, in 2011 on charges of murder and persecution, but ICC appeals judges this year said authorities in Libya can put him on trial for similar charges.
Human rights groups have demanded that Libya turn over Gadhafi to the ICC as concerns grow about the potential for further abuses in the country amid the violence.
"Security Council members should make clear that the state of impunity in Libya needs to end," Richard Dicker, international justice director at Human Rights Watch, said in a statement today. "Turning a blind eye to justice has been a main driver for the country's current instability.