* Construction equipment makers fall on Nomura's downgrades
* Solar-related shares up on govt renewable energy plan
* Nikkei's support seen at 9,405.19-trader
By Ayai Tomisawa
TOKYO, May 23 (Reuters) - The Nikkei stock benchmark fell 1 percent on Monday after construction machinery and related parts makers tumbled on a brokerage's downgrades and as a flare-up in euro-zone debt worries hurt overall sentiment for risk assets.
Analysts said that trading may be thin as there are few buying catalysts and as foreign buying may wane on renewed concerns about the global economy.
But solar-power equipment makers bucked the trend on a Nikkei report that the Japanese government may this week announce a plan to make solar panels compulsory on the roofs of all new buildings by 2030.
"Foreigners are selling construction equipment makers after Nomura downgraded them on worries about a slowdown in demand in China," Katsuo Suzuki, a sales trader at Instinet.
In mid-morning trade, the benchmark Nikkei average fell 1.3 percent to 9,483.49, breaking recent support around 9,500.
The broader Topix shed 1.1 percent to 818.91.
Suzuki said the next immediate support line for the Nikkei is 9,405.19, an intraday low marked on April 19.
Komatsu Ltd slid 6 percent to 2,379 yen and was the heaviest traded stock on the main board by turnover after Nomura Securities cut its target price by 11 percent, although it kept its "buy" rating.
Hitachi Construction was cut to "reduce" from "neutral," which dragged down the stock by 4.8 percent to 1,697 yen, while Kawasaki Heavy , a maker of hydraulic equipment was cut to "neutral" from "buy" sending the stock down 5.2 percent to 290 yen.
The euro lost nearly 1 percent over disagreements on how to handle debt problems in Greece and ahead of a Spanish regional election. [ID:nLDE74F1GL]
Among solar panel stocks, Sharp Corp rose 1.8 percent to 739 yen, and panel equipment maker Ulvac gained 4.1 percent to 1,971 yen while Ishii Hyoki , a maker of silicon wafers for solar cells, added 2.8 percent to 880 yen.
"Some of the solar stocks have not fallen since the March earthquake on hopes that renewable energy will be promoted after the country was hit the nuclear crisis," said Yumi Nishimura, a senior market analyst at Daiwa Securities."
"These stocks may continue to attract buying."
While the Nikkei has shed about 9 percent since the March quake, Ishii Hyoki has added 8 percent and Ulvac has only shed 0.4 percent. (Editing by Edwina Gibbs)