NATO has stepped up its airstrikes in Tripoli in an apparent attempt to weaken Gadhafi's chief stronghold, the Libyan capital, and potentially target the leader himself.

The international warrants could further isolate Gadhafi and his inner circle and potentially complicate the options for a negotiated settlement. But they also could harden Gadhafi's resolve to stand and fight, since the legal action has been seen in Libya as giving NATO more justification to go after him.

Because the United Nations Security Council ordered the ICC investigation, UN member states would be obliged to arrest him if he ventured into their territory.

Prosecutor Luis Moreno-Ocampo said he was seeking the request of the UN didn't result in the desired arrest. Although Sudanese President Omar al-Bashir has been indicted for crimes including genocide in the Darfur region of Sudan, at least three countries have let him visit without detaining him.

Asked why he has not launched similar investigations into other Arab uprisings, Moreno-Ocampo said that no such action had been requested by the Security Council, as it was in the case of Libya.

Regimes in Egypt and Tunisia - which eventually were overthrown - were accused of human rights violations in their efforts to end street demonstrations. Similar charges have been leveled at the rulers of Bahrain, Yemen and Syria.

In London on Monday, a British defense minister, Nick Harvey, told legislators he believed it was likely the court would seek to charge Syrian President Bashar Assad over his government's violent crackdown on protests.

He said, however, that the opposition would like to see Gadhafi tried first in Libya, then before the world body.

Under Gadhafi's more than four decades in power, the regime "has committed many crimes against the Libyan people, and the Libyan people want to see him punished for that," Ghoga said.

In Brussels, NATO said Moreno-Ocampo's announcement was "further proof that the international isolation of the Gadhafi regime is growing every day."

NATO spokeswoman Oana Lungescu added: "It is hard to imagine that a genuine transition in Libya can take place while those responsible for widespread and systematic attacks against the civilian population remain in power."

She said NATO's mission to protect civilians in Libya would remain unchanged.

Members of TV said a number of people were killed and wounded. It did not elaborate.

At least three explosions believed caused by NATO strikes shook windows around the Libyan capital. It was not immediately clear what was targeted, but a government spokesman said he believed the jets were aiming for Gadhafi's compound.

The rebel forces appeared to have expanded their hold on Misrata, the only major opposition stronghold in western Libya. Most of the rebel forces are concentrated in the east.

A video posted Sunday on the Libyan rebels' Facebook page showed more than 200 SUVs and rebel vehicles at the southeastern gate of Misrata. That would give the rebels tighter control of the access points into the city.

Abdel Salam, a rebel militia fighter, told The Associated Press that opposition forces were able to advance on the location after NATO bombings in recent days. Reporters have had a difficult time reaching the city, and it was not possible to verify the claims independently.

Misrata has been the focus of an international aid effort to help thousands of civilians caught in the fighting. Some 1,000 people have been killed in the two-month siege of the rebel-held enclave by Gadhafi's forces.

Moreno-Ocampo said the targeting of opposition figures is continuing in areas under Gadhafi's control.

"Gadhafi's forces prepare lists with names of alleged dissidents. They are being arrested, put into prisons in Tripoli, tortured and made to disappear," he said.

"These are not just crimes against Libyans, they are crimes against humanity as a whole," he added.

Rights activists welcomed Moreno-Ocampo's move.

"The ICC prosecutor's request acts as a warning bell to others that serious crimes will not go unpunished," said Richard Dicker, international justice director at Human Rights Watch. "It's a message to those responsible for grave abuses that they will be held to account for their actions."

In another development, Libyan spokesman Moussa Ibrahim said late Monday that four reporters held for the past few weeks by the Libyan government will face trial and likely be released.

The identities of the reporters were not immediately available, but Ibrahim said they included at least two Americans and a Spaniard.

They will appear before a judge in an administrative court on Tuesday, Ibrahim said.

"It's not a big deal. They should be fined a certain amount of money .... and then they should be released," he said.

Among the reporters missing in Libya and thought to be in government custody are James Foley, a photojournalist working for GlobalPost, a Boston-based news agency; Clare Morgana Gillis, who was covering the fighting for The Atlantic and USA Today, and Manu Brabo, a Spanish photojournalist was taken with them. They were captured April 5.

It was not clear that Ibrahim was referring to those four. He said a South African journalist reported to have been captured by Libyan forces has not been found.