Police beefed up patrols around national landmarks Wednesday, a day after the District of Columbia's police chief declared a crime emergency in response to a string of violence that included the killing of a British activist.

At least 14 people have been killed in Washington already this month, and in the last 30 days robberies have risen 14 percent and armed assaults have jumped 18 percent. Last year, homicides in the city fell to a 20-year low of 195.

Police Chief Charles Ramsey's emergency declaration allows commanders more flexibility to adjust officers' schedules and reassign them to high-crime areas.

"That's a short term solution," Ramsey said Wednesday. "Long-term is a lot more complicated than that, and it's going to take a whole lot more than the police."

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Just hours after the declaration, two groups of tourists were robbed at gunpoint on the National Mall, both by men dressed all in black. The U.S. Park Police, who patrol the Mall and are separate from the D.C. police, posted more officers in the area in response.

"We're going to reallocate our resources. We're going to see what improvements we can make," said Park Police Sgt. Scott Fear.

Park Police were looking for connections between the robberies and three similar incidents in the area in late May. There have been no arrests in any of those cases.

Park Police Chief Dwight Pettiford met Wednesday with Eleanor Holmes Norton, the city's delegate to Congress, to discuss the deployment of officers. Norton said the Interior Department had ordered the Park Police to assign officers at fixed positions, rather than walk beats.

Those killed in the recent violence include British activist Alan Senitt, a volunteer for the potential presidential campaign of former Virginia Gov. Mark R. Warner. His throat was slit Sunday in the affluent Georgetown area, and police say his attackers attempted to rape his companion.