1.   On Tuesday, the standoff exploded in gunfire.

2.   Authorities have barred the marchers, and the standoff has exploded into five nights of street violence.

3.   The nine-day standoff exploded Tuesday when gunboats of the two Koreas exchanged fire.

4.   The standoff exploded into a shootout last Tuesday when South Korean navy ships tried to bump and push North Korean patrol boats back to their own waters.

5.   The standoff exploded into an armed conflict Tuesday when warships of the two Koreas exchanged fire.

6.   The standoff exploded Tuesday when warships of the two Koreas exchanged fire.