The Philippine government says its largest warship is engaged in a standoff with Chinese surveillance vessels that blocked it when it attempted to arrest Chinese fishermen anchored at a South China Sea shoal where both sides claim sovereignty.

Foreign Secretary Albert Del Rosario on Wednesday summoned Chinese Ambassador Ma Keqing to resolve the dangerous impasse diplomatically. His office said in a statement that the Scarborough Shoal "is an integral part of Philippine territory'' and Filipino authorities would assert sovereignty over the offshore area.

The shoal lies off the northwestern Philippine province of Zambales. China and the Philippines have been disputing ownership of the shoal, in addition to the Spratly Islands and other areas in the South China Sea. (AP)