Gulf nations send forces to Bahrain A Bahraini nurse (front right) walks with anti-government protesters heading onto the streets to await Saudi forces on Monday in Manama (AP photo) MANAMA/WASHINGTON (Agencies) - A military force from Saudi Arabia and other Gulf nations moved into Bahrain Monday to help restore security after a month of anti-regime protests, the Associated Press reported. The force marked the first cross-border military operation to quell unrest since the Arab world's rebellions began in December. Bahrain's main opposition groups immediately denounced the outside intervention as an "occupation" that pushed the Gulf kingdom dangerously close to a state of war. Bahrain's army urged citizens to fully cooperate with the Gulf troops, according to Agence France-Presse. "The Bahrain Defence Force General Command calls on all citizens and residents to cooperate fully and to welcome the GCC Peninsula Shield Force," said a government statement. State television aired footage of unmarked military vehicles rolling into Bahrain across a causeway linking the archipelago with neighbouring Saudi Arabia, AFP reported. Meanwhile, Reuters reported that the White House does not consider the forces entry into Bahrain an invasion. â€œThis is not an invasion of a country,â€ White House spokesman Jay Carney told a news briefing on Monday. â€œWe urge the government of Bahrain, as we have repeatedly, as well as other GCC countries, to exercise restraint,â€ Carney added. The Shiite protests in Bahrain have ignited fears of a potential foothold for Shiite heavyweight Iran to increase influence in the Gulf region. â€œThe Bahrain government asked us yesterday to look at ways to help them to defuse tension in Bahrain,â€ United Arab Emirates Foreign Minister Abdullah Ben Zayed Al Nahyan said in Paris. He said they sent 500 Emirati police and the Saudis and others also sent forces â€œto get calm and order in Bahrain,â€ AP reported. The strife in Bahrain escalated dramatically over the weekend just as US Defence Secretary Robert Gates arrived to urge its leaders - key Washington allies - to heed at least some of the demands for change. A Saudi security official said the Gulf units dispatched to Bahrain come from a special force within the six-nation Gulf Cooperation Council (GCC). He did not give details on the size or national breakdown of the force - estimated in some reports at about 1,000 strong - but said they were deployed by air and road and will help protect key buildings in the strategic nation, which hosts the US Navyâ€™s 5th Fleet. The official spoke on condition of anonymity because he was not authorised to brief media. The GCC members are Bahrain, Saudi Arabia, Kuwait, Qatar, Oman and the United Arab Emirates. The Gulf Daily News, which is close to Bahrainâ€™s rulers, said the outside forces would protect sites such as electricity stations and oil facilities. The arrival of the military force comes a day after some of the most widespread chaos in the monthlong series of protests and clashes that have left seven dead and the nation deeply divided. On Sunday, protesters blocked the main route to Bahrainâ€™s important financial district and battled pro-government mobs at the main university, which has cancelled classed indefinitely. A group of pro-government lawmakers Monday urged Bahrainâ€™s king to impose martial law and claimed â€œextremist movementsâ€ were trying to disrupt the country and push it towards sectarian conflict. A coalition of seven Shiite-led opposition factions pledged to demand a UN investigation into the Gulf leadersâ€™ decision to send in the special force for an internal conflict. The unit had been deployed in the past to Kuwait, including during the 1991 US-led campaign to drive out Saddam Husseinâ€™s troops and before the 2003 invasion of Iraq. â€œWe consider that any military force or military equipment crossing the boundaries of Bahrain - from air, sea or land - an occupation and a conspiracy against the people of Bahrain,â€ said a statement from the opposition groups. In a series of Twitter messages, Bahrainâ€™s prime minister, Sheikh Khalifa Ben Salman, lashed out at the Shiite-led protesters. â€œWhat we are witnessing in Manama is no peaceful protest,â€ he wrote. â€œItâ€™s wanton, gangster style takeover of peopleâ€™s lives.â€ The protesters claim Shiites are being blackballed from key government and security posts. They also strongly object to government policies that they claimed give citizenship and jobs to Sunnis from other Arab countries and South Asia as a way to offset the Shiitesâ€™ demographic edge. The main opposition groups have called for the Sunni rulers to give up most of their powers to the elected parliament. But, as violence has deepened, many protesters now say they want to topple the entire royal family.