The U.N. Mideast envoy says threats by Hamas to continue building tunnels into Israel do "not help" reconstruction efforts in war-battered Gaza Strip.

Nikolay Mladenov spoke on Wednesday during a visit to Gaza. He toured Shijaiyah, one of the hardest hit areas in the 2014 war between Hamas and Israel.

His remarks appeared to be a veiled criticism aimed at the Islamic militant group, which has struggled to balance its hard-line anti-Israel ideology and the pragmatic needs of ruling the territory.

Hamas officials have pledged to continue building tunnels along the Israeli border, even after recent collapses killed 10 Hamas fighters. Israel views the tunnels as a top threat.

Reconstruction in Gaza has been sluggish. Mladenov says only a third of funds pledged by international donors has been received.