Sept 18 (Reuters) - Taiwan scrambled fighter jets on Friday as 18 Chinese aircraft buzzed the island, including crossing the sensitive mid-line of the Taiwan Strait, in an escalation of tensions as a senior U.S. official held talks in Taipei.

Following are key Reuters stories on the strained relations between the two sides and the role played by the United States, Taiwan's most important ally:

TOP STORIES > Taiwan jets scramble as Chinese planes buzz island > China says it's conducting military exercises near Taiwan Strait > Taiwan urges China to show restraint > Top U.S. diplomat for East Asia calls China 'lawless bully' > China says will make 'necessary response' to US official's Taiwan visit > China says military drills near Taiwan were a 'necessary action'

EXCLUSIVES/ANALYSIS > 'Polishing the gun': China, U.S. tensions raise Taiwan conflict fears > EXCLUSIVE-U.S. pushes arms sales surge to Taiwan, needling China

FACTBOXES > FACTBOX-Taiwan, China and the United States > FACTBOX-Key facts on Taiwan-China relations (Compiled by Raju Gopalakrishnan and Ben Blanchard)