Libya's political crisis has deepened as armed groups surrounding two ministries in the capital said they had formed an alliance to present an expanded list of six demands that included the resignation of Prime Minister Ali Zeidan.

The armed groups initially demanded that parliament pass the "political isolation law" banning senior officials, who held a senior position under late Muammar Gaddafi, from office, and members had hoped the vote would be enough to dislodge the gunmen from their positions at the government ministries.

Instead, the groups have settled in and expanded their list of demands, which they presented to Reuters news agency on a printed notice late on Wednesday.

The additional demands included Zeidan's resignation, the freezing of a recently released state budget and the right to form a committee to take charge of the Foreign Ministry.

Rival warning

In a separate development, a rival coalition that said it supported the government warned those stationed at the ministries it was prepared to use force to dislodge them.

"If you do not respond to our demands, we will form a common national force from all the cities of Libya to handle this situation," the group said on Wednesday.

Its members included federalists in eastern Cyrenaica and leaders of former rebel groups in a number of towns including Benghazi in the east.

Zeidan, for his part, promised the government would stick to plans to bar anyone who held a senior position under Gaddafi and said some ministers would have to be replaced under legislation passed on Sunday.

Zeidan defended the armed groups, saying they had a right to express their views as they saw fit.

"We don't have militias in Libya, we have revolutionaries," he told a news conference.

The prime minister also denied that parliament had bowed to their pressure, insisting the new law was necessary to protect the ideals of the revolution, adding he hoped the world would appreciate Libya's exceptional circumstances.

"With any law passed, there are some positive and some negative aspects, and we need to accept the negatives," he said.