* STOXX 600 ends flat, Spain's IBEX down 0.7 pct
* Higher commodity prices support miners
* Warnings hit Siemens Gamesa, ConvaTec, Husqvarna
* Hochtief bounces after upgrade (Adds closing prices)
MILAN, Oct 16 (Reuters) - Spanish stocks lagged behind a broadly flat European market on Monday as the Catalonia crisis and a profit warning from renewables energy firm Siemens Gamesa weighed.
Spain's country index IBEX fell 0.7 percent while the pan-European STOXX 600 benchmark added a symbolic 0.01 percent, staying near the four-month highs hit last week as optimism over global growth offset growing political worries.
"Spanish stocks have come under pressure again", said CMC Markets analyst Michael Hewson after Catalan leader Carles Puigdemont failed to clarify whether he had declared independence from Spain last week, possibly paving the way for the central government to take control of the wealthy region.
Spanish banks Caixa, Sabadell and BBVA took some of the heat, falling between 1.7 and 2.8 percent but Siemens Gamesa was the top loser, down 6.3 percent after it warned on profit on Friday.
Top faller on the STOXX was ConvaTec, which posted a dramatic 26.6 percent collapse after the British medical technology company cut its full-year organic revenue growth forecast.
A sales warning also sent shares Husqvarna down 4.9 percent.
On the winners' side, France's Ipsen closed with a 6.1 percent rise after reporting positive news on a liver cancer clinical trial.
Germany's Hochtief rose 3.5 percent after an upgrade to "buy" from "hold" from Bankhaus Lampe on prospects of a potential acquisition of Spanish motorway firm Abertis in a takeover battle with Italy's Atlantia.
"If Hochtief acquires the toll operator Abertis, the upside potential for shares should be considerable and lift the price above euro 200," Bankhaus Lampe said.
Higher metal and crude oil prices supported the broader market, sending heavyweight mining stocks like Glencore , Rio Tinto and BHP up between 0.8 and 1.5 percent. (Reporting by Danilo Masoni; Editing by Toby Chopra)