ALI MOORE: The king in Bahrain has declared a three month state of emergency as anti-government protests continue in the Emirate.

Troops from Saudi Arabia and the United Arab Emirates have arrived in Bahrain to help the country's ruling monarchy restore law and order.

The neighbouring Gulf states say it's not an invasion but Bahrain's opposition groups have described the arrival of foreign forces as an occupation.

The ABC's Middle East correspondent Anne Barker reports.

ANNE BARKER: Saudi armed forces rolled into Bahrain, across the causeway which links the two Gulf kingdoms.

One thousand Saudi troops and 500 police from the United Arab Emirates arrived as clashes between anti-government protesters and Bahrain's security forces intensified.

Yesterday dozens of protesters were injured as security forces loyal to the Sunni royal family battled thousands of Shiite demonstrators, calling for democratic reforms.

At a meeting in Paris with the US Secretary of State, Hillary Clinton, the Emirates foreign minister said his country was simply answering a call for help.

ABDULLAH BIN ZAYED, UNITED ARAB EMIRATES FOREIGN MINISTER: The Bahrain government asked us yesterday to look at ways to help them to diffuse the tension in Bahrain.

ANNE BARKER: But Bahrain's opposition says the arrival of foreign forces amounts to an occupation.

AL-WAAD IBRAHIM SHERIF AL SAYD, OPPOSITION LEADER (translated): We say to our brothers in the Gulf, your army is welcome when our country faces danger from the outside, but we will consider you part of an occupation, when you come to oppress the people.

ANNE BARKER: Bahrain is home to the United States fifth fleet, despite a close relationship with the Bahrain Government, the US has been caught off guard.

The White House was only advised at the last minute about the deployment of foreign troops, leaving an awkward moment for the US Secretary of State.

HILLARY CLINTON, US SECRETARY OF STATE: The UAE is currently the head of the Gulf co-operation council and he is here representing the GSC so we will have a very comprehensive discussion.

ANNE BARKER: The White House stopped short of calling for the foreign troops to leave.

JAY CARNEY, WHITEHOUSE SPOKESMAN: We are calling on the Saudis to show restraint and we believe political dialogue is the way to address the unrest that has occurred in the region.

ANNE BARKER: Shiites in Bahrain account for 70 per cent of the population and have long complained of discrimination by the Sunni Dynasty.

Some opposition groups are calling for the Sunni rulers to give up their powers in the partially-elected parliament. But as the violence increases many protesters are now calling for the entire royal family to go.

The arrival of foreign forces suggests Bahrain's royal family can no longer hold onto power without their support.

Anne Barker, Lateline.