Clerk stabbed: A convenience store clerk was stabbed in the abdomen during an apparent robbery yesterday in Prince George's County, police said.

Police said the clerk, whose name was not released, was taken to a hospital, where she had surgery and was expected to recover from her wounds.

The clerk was stabbed shortly after 11:30 a.m., after two men announced a robbery at the Mini-Mart in the 2100 block of Brooks Drive in District Heights, said Sgt. Tammy Sparkman, a police spokeswoman. Sparkman said the men ran away after the stabbing, but it was unclear whether they took any money.

Police vehicles rammed: A Rockville man rammed four occupied police vehicles with his pickup early Friday after allegedly writing a letter in which he threatened to kill Montgomery County police officers, police said yesterday.

Da Tan Yang, 53, of the 14000 block of Pellita Road in Rockville, is in police custody at a local hospital for mental evaluation, Montgomery County police said. Police said they have a warrant for Yang's arrest on charges of first-degree assault and malicious destruction of property, which they said they plan to serve when Yang is released from the hospital.

On Thursday, a letter addressed from Yang's Rockville house arrived at a police substation in Wheaton, police said. Police said the letter, written in Chinese, contained a threat to kill police with an automatic weapon. Police were dispatched to Yang's house, and Yang was pulled over in his 2004 Ford F150 but refused police orders and drove away, police said. He was detained after ramming the police cars a short time later. No one was hurt, they said.

Compiled from reports by staff writers.