Patent firm IPCom said it sued about 100 German retailers for patent infringement, saying they continued selling phones made by HTC beyond a deadline it had imposed earlier this month.

IPCom said in a statement on Thursday that it sent the retailers cease and desist requests on December 6, asking them to stop selling HTC's 3G handsets by December 20 following a ruling by a German district court in 2009 in a patent dispute with HTC.

Since this deadline has passed without any of the retailers complying, IPCom has sued them for infringement of patent #100A themselves, IPCom said.

A court in Mannheim, Germany, ruled in February 2009 against HTC in a patent fight with IPCom, allowing an injunction against sales of HTC phones using UMTS technology, and setting a penalty of up to 250,000 euros ($326,200) each time the injunction was contravened.

In late November, a court in Karlsruhe, Germany, said the injunction against HTC smartphone sales in Germany could be enforced after HTC had dropped an appeal.

Possible fines from the German court could cost millions of euros and hurt HTC's position in one of its key markets. The company sells around 2 million smartphones a year in Germany, some 4-5 percent of the group's total, according to research firm IDC.

($1 = 0.7664 euros)

(Reporting by Christoph Steitz and Tarmo Virki; Editing by David Cowell)