* ASML files countersuits as patent battle heats up vs Nikon
* More suits threatened to follow in the United States
* Nikon considering response after suits vs ASML this week
* ASML has 80 pct of revs in market vs Nikon, Canon - Fitch (Adds Nikon statement)
By Wout Vergauwen
April 28 (Reuters) - ASML, the world's third largest semiconductor equipment maker, said on Friday it had counter-sued rival Nikon, after the Japanese company launched a wide-ranging patent battle against the Dutch company this week.
ASML's lawsuits involve semiconductor manufacturing equipment, flat panel display manufacturing equipment and digital cameras.
They were brought in Japan by ASML on its own and jointly with its partner Carl Zeiss, a German maker of optical systems and medical devices, ASML said in a statement.
ASML dominates the market for lithography machines used by the world's biggest chipmakers to make circuits ever smaller, faster and more powerful. It generates around 80 percent of revenues in that market, ahead of No.2 player Nikon and No.3 Canon Inc, according to ratings agency Fitch.
The round of lawsuits and countersuits follows efforts to renegotiate a patent deal between ASML and Nikon that expired in 2014 and threatens to revive patent battles that stretch back to the turn of the century.
Patent wars are infrequent in the technology industry, which depends on thousands of patents that companies frequently cross license to rivals, while reserving their most strategic intellectual property to create proprietary products.
Intense competition sometimes spills over into costly legal battles as seen in a string of patent wars among smartphone makers in recent years.
ASML, Nikon and Zeiss settled litigation in 2004 after the International Trade Commission found ASML had not infringed Nikon patents.
ASML, which denies infringing any of Nikon's patents, said it was left with no choice but to file counter-suits.
Nikon, the world's eighth-largest chip equipment maker, said on Monday it had filed a patent case against ASML and Zeiss, accusing them of using its lithography technology without permission (reut.rs/2pplglg).
The Tokyo-based company filed a string of suits in the Netherlands, Germany and Japan.
"Now that Nikon has decided to take this dispute to court, we also have to enforce our patent portfolio, and we will do this as broadly as possible," ASML Chief Executive Peter Wennink said in a statement, adding it had tried for years to reach a cross-licensing agreement with Nikon.
Nikon said it had not yet received the complaints.
"ASML and Zeiss’s retaliatory lawsuits are a predictable litigation tactic," Nikon said in a statement, adding its own lawsuits targeted products that account for 76.3 percent of ASML sales last year, worth about 3.5 billion euros.
Additional suits will be brought in the United States, ASML said. (Reporting by Wout Vergauwen in Gdynia; Additional reporting by Sam Nussey in Tokyo and Eric Auchard in London; Editing by Adrian Croft and Mark Potter)