The Government has expelled five diplomats from the Libyan embassy in London because they "could pose a threat" to national security.
Updating the Commons on the London conference on Libya, Foreign Secretary William Hague told MPs: "To underline our grave concern at the (Gaddafi) regime's behaviour, I can announce to the House that we have today (Wednesday) taken steps to expel five diplomats at the Libyan embassy in London, including the military attache.
"The Government also judged that were these individuals to remain in Britain, they could pose a threat to our security."
Earlier at Prime Minister's questions, David Cameron said the UK would not rule out arming Libyan rebels to protect civilians.
He said the UN Security Council resolution would not block the supply of weapons "in certain circumstances" despite an arms embargo on Libya.
Tornados had destroyed artillery and an armoured vehicle near Gaddafi's home town Sirte during the latest wave of bombings, he said.
Mr Cameron told MPs: "It is an extremely fluid situation but there is no doubt in anyone's mind the ceasefire is still being breached and it is absolutely right for us to keep up our pressure under UN Security Council 1973.
"I can confirm to the House the coalition took action yesterday against regime forces harassing civilian vessels trying to get into Misrata and yesterday and overnight the RAF flew 24 sorties. Tornado aircraft destroyed artillery and an armoured fighting vehicle near Sirte."
Responding to a question from Labour leader Ed Miliband on arming rebels, he said: "I've said before in this House that we must do everything to comply with both the Security Council resolutions. And as I've told the House the legal position is clear that the arms embargo applies to the whole territory of Libya.
"But at the same time UNSCR 1973 allows all necessary measures to protect civilians and civilian-populated areas. Our view is that this would not necessarily rule out the provision of assistance to those protecting civilians in certain circumstances. We do not rule it out but we have not taken the decision to do so."