LONDON, July 30 (Reuters) - European shares closed lower on Wednesday, little moved by strong U.S. growth data, after weak earnings reports from cement-makers and concerns about a possible escalation of the conflict between Russia and Ukraine.
Holcim's and HeidelbergCement's shares fell 4.8 percent and 2.9 percent respectively, leaving the STOXX Europe 600 constructions and materials index down 1.4 percent.
The pan-European FTSEurofirst 300 index provisionally closed 0.5 percent lower at 1,366.69 after a choppy session.
The index extended losses in the afternoon as NATO said the number of Russian troops and weaponry along the border with Ukraine was increasing to "well over 12,000".
Fighting between Moscow-backed rebels and government troops has intensified since a Malaysian airliner was shot down earlier this month.
"(The threat of) war is the main drag on markets this afternoon," Mike Reuter, a broker at Tradition, said. (Reporting By Francesco Canepa; Editing by Lionel Laurent)