A barely week-old truce between Israel and the Hamas rulers of Gaza frayed further on Thursday when Palestinian militants launched two rockets against Israel, and Israel prevented goods from entering Gaza for a second day.

One of the rockets fell harmlessly in an open area across the Israeli border, a military spokesman said. No details were available about the second.

Israel sealed the border crossings on Wednesday in response to a rocket attack on Tuesday, the first serious breach of the Egyptian-brokered truce. In light of the latest rocket fire, Israeli officials were still deliberating Thursday about when to reopen the crossings.

Neither side talked of calling off the cease-fire, but each accused the other of violating the agreement, which took effect on June 19.

People in Gaza have reported that Israeli troops along the border opened fire to drive Palestinian farmers away from agricultural land near the border fence. Shots from Israeli Navy vessels intended to keep Palestinian fishermen within proscribed areas close to the shore also have been reported.

A United Nations official in the region said two elderly Palestinian men were seriously wounded by the army gunfire, including an 82-year-old farmer who was shot Wednesday east of Khan Yunis, in southern Gaza.

Israeli military officials, who were speaking on condition of anonymity under army rules, acknowledged that forces had fired into the air on Wednesday as a warning when a group was spotted approaching the border fence east of Khan Yunis. But the officials said there was no record of any casualties. They said that they could not confirm any other shootings.

Before the cease-fire, militants often laid, or tried to lay, explosives along the border fence. The army is also on guard against infiltrations.

Al Aksa Martyrs Brigades, a group nominally associated with the mainstream Fatah organization led by President Mahmoud Abbas, said it fired the rockets on Thursday. Islamic Jihad claimed responsibility for the three rockets fired Tuesday, saying that it was retaliating for an Israeli raid that killed one of the group’s senior commanders in the West Bank.

The cease-fire applies only to Gaza, but some smaller groups have reserved the right to respond to any deadly Israeli raids in the West Bank — a point over which informal truce understandings have broken down in the past.

Under the terms of the current agreement, Israel expects Hamas to enforce a complete cessation of fire from Gaza and to stop smuggling in weapons. Hamas has demanded a halt to all Israeli military action in Gaza and the lifting of the border blockade that Israel imposed after Hamas took over the coastal territory a year ago.

A spokesman for Al Aksa Martyrs Brigades said the rocket attack on Thursday was in response to “Israeli violations.” He added, “Any calm deal must end Israeli attacks on our people in the West Bank, too.”

Said Siam, a Hamas security chief in Gaza, met representatives of the militant groups there on Wednesday to discuss ways of respecting the cease-fire and how to respond to Israeli military actions in the West Bank. Daoud Shihab, a spokesman for Islamic Jihad, said that it would start to coordinate its responses with Hamas.