Two protesters got on to the roof of the Bahraini embassy in London on Monday and unveiled a banner in support of a jailed activist on hunger strike.
Abdulhadi al-Khawaja, a Shiite who was sentenced with other opposition activists to life in jail over an alleged plot to topple the Sunni monarchy during a month-long protest in 2011, began a hunger strike on the night of February 8-9.
The pair also waved the Bahrain flag from the top of the building in the plush Belgrave Square, which houses several embassies.
"We were made aware at 1:35pm (1235 GMT) of two protesters on the roof of the Bahraini embassy in Belgrave Square," a police spokesman told AFP. "Officers are in attendance and local road closures are in place."
In Manama, the foreign ministry warned London that it was dealing with "terrorists."
It urged authorities "to deal with the situation immediately, take necessary and fast action required in such cases, disembark the terrorists from the roof ... and enforce the working law proceedings."
The foreign ministry, quoted by state news agency BNA, said "it stresses that the British police are dealing with terrorists at the moment in an attempt to have them disembarked from the roof of the embassy building."
It urged "the UK government to undertake full legal responsibility of providing the necessary protection to the embassy building and diplomats and members of staff," according to the Vienna Convention on diplomatic relations.