A Palestinian teen has been killed and two other men wounded by Israeli fire in southern Gaza, according to health officials.

Gaza Health Ministry spokesman Ashraf al-Qidra said 18-year-old Yousef Abu Athira was killed before dawn on Wednesday by Israeli artillery fire east of Rafah.

He said two others sustained shrapnel wounds and were taken to Abu Yousef al-Najjar Hospital in Rafah.

The Israeli army, which had been carrying out training exercises near the border overnight, said it detected three people near the security fence separating Gaza and Israel and fired at them, according to a military spokeswoman.

But Yasser Abu Athira, the killed teen's cousin, said the 18-year-old was on the farming land that his family owns.

"We heard the noise of about 15 shells that came down. After a while, we found out that it was Yousef. The Israeli army said he was trying to get into Israel, but we completely deny that claim," he told Al Jazeera.

"We are very angry and we blame this on the occupation and the Israeli army. He was not armed and he is not part of any faction."

READ MORE: Gaza's healthcare crumbling under Israeli siege

Gaza has been under a decade-long siege imposed by Israel following Hamas' election victory and subsequent takeover of the enclave in 2007.

Israel's military said that some 2,000 reserve soldiers had since Sunday been performing military exercises around Gaza Strip.

Tareq Rishmawi, spokesperson for the Palestinian government, denounced the Israeli army's large-scale exercises over the past few days and called on the international community to end the systematic "Israeli assaults".

"The continuation of the unacceptable Israeli siege on Gaza, exceeding 10 years, and continuing assaults on our people is a violation of international human rights law," he said.